I spend a couple of weeks each summer in Bar Harbor, Maine, indulging in a fantasy made possible by the shared ownership of a turn-of-the-century vacation "cottage" overlooking a bay of the Atlantic Ocean. The cottage -- some would call it a white elephant -- contains nearly 20,000 square feet of space.

Part of the fantasy is knowing that practically no one builds houses like this anymore, that we who own it now can only imagine life here six or seven decades ago. Having no television set in the house helps.

Purchased in 1975 after being marked down to a price below its original 1909 construction cost, this villa-by-the-sea was designed by Guy Lowell, architect for the Boston Museum of Fine Arts. Some 150 Italian craftsmen built the second-Renaissance revival Italianate structure -- stucco walls, carved plaster decoration, red roofing tiles -- and now it is listed on the National Register of Historic Places.

The cottage encompasses several dozen high ceilinged rooms, including reception and billiard rooms and a dining room that demands a banquet at every sitting. Each major space and bedroom has its own distinctive marbled and manteled fireplace, 13 in all. Nine bedrooms and seven baths comprise the second floor. The third floor, a dormered attic, consists of former servants' rooms; today it's the kids' dormitory.

Our "cottage," along with the many other Victorian and post-Victorian houses on Mt. Desert Island, are vivid reminders of how much the conception of "house" has evolved over the last hundred years. And it's not style, but content, that's been transformed.

Upper and upper-middle class houses of the 19th and early 20th centuries were not just ornate and capacious vessels for exhibiting, either ostentatiously or subtly, the taste, affluence and acquisitions of their owners.

They embodied how people behaved and interacted, how economic and human resources were controlled and allocated, and what technologies were available.

For a long time, the ideal house was a collection of separate rooms exclusively dedicated to separate activities -- library, parlor, dining room, kitchen, scullery, breakfast room, billiard room, sewing room. This reflected long-standing, well-understood patterns of family and social intercourse. Everyone, especially children, guests and servants, knew when and where they could go and how to behave when they got there.

But with increased democratization and relaxed norms of behavior, informality supplanted formality. The need for differentiation and hierarchy, both of people and space, within the home seemed less compelling. Thus, combining functions and spaces, a 20th-century idea often necessitated by economic constraints, was inevitable. And it was reinforced further by modern architectural theories about the aesthetic merits of visual overlapping and spatial continuity.

Thus, activities previously kept separate began to merge in the spirit of communality. In some houses, only bedrooms and baths remained truly self-contained and private. For one- or two-person households, even separate bedrooms became optional, giving rise to the efficiency or, more descriptively, the zero-bedroom apartment.

Technology likewise proved to be a forceful catalyst in reshaping modes of living and, consequently, how we shape houses.

For example, the high ceilings of yesteryear not only provided visual loftiness and generous wall space for hanging pictures, they also contributed to thermal comfort in summertime. Cool air sank to the floor and warm air rose to the ceiling. During winter months, this disadvantage presumably could be overcome by fireplaces, stoves and steam heat.

And until recent times, bathrooms and kitchens always were located on exterior walls where they had direct access to natural light and indispensable fresh air. But the advent of automated heating, ventilating and air conditioning systems eliminated the necessity, though not the desirability, of high ceilings and windows in bathrooms and kitchens.

Dozens of electrically powered gadgets have been invented to make domestic life easier -- when they don't break down -- and have most profoundly transformed the kitchen. Appliances for storing, processing, cooking and disposing of food have radically altered the place and purpose of what used to be the symbolic locus of drudgery and servitude, primarily for women.

The kitchen used to be an isolated space, off limits certainly to guests, the labor-intensive realm of home-bound housewives or servants in affluent households. But the days of cheap labor have disappeared. Simultaneously, the art -- and potential fun -- of cooking was discovered. For many, cooking and eating turned into lifelong hobbies. In the late 20th century, sales of cookbooks outstripped all other types of books.

With kitchencraft facilitated by new appliances, kitchens could be both smaller and more efficient. Yet many people prefer spending lots of time in or near the kitchen. Thus, the kitchen, not the living room, can become the center of communal activity, the new symbolic hearth. Kitchens and their attendant spaces can become a place of assembly and ritual, the site to which both host and guest are drawn. What contemporary homeowner would not like to have a bigger, better kitchen?

Some homeowners may wonder if they even need living rooms -- the traditional parlor filled with unmussed furniture. A spacious, beautifully appointed and equipped "designer" kitchen, flanked by sitting, eating and entertainment areas, can suit perfectly the informal life style of modern families who rarely entertain formally.

The kitchen-centered house may be more appealing than ever when all adults in a household work full-time. Perhaps houses and apartments of the future will be organized around a giant kitchen-social-entertainment center, complete with video, audio, communication and computer facilities.

Add a couple of automobiles and their housing to the ensemble, and you get a contemporary villa in which the garage may become the biggest single architectural volume, and, with the kitchen, the biggest interior space. Indeed, the garage appendage of many 20th century houses was deemed unnecessary in the villas of yesteryear. Cars, like horses and carriages, were stabled in separate buildings.

Suburban houses often are compromises between old and new, attempts to retain the multiple-room memory of bygone areas while incorporating features responding to contemporary life styles, behavior and technology. But affordability demands that today's rooms be small, that porches be vestigial, that furniture be reduced in scale to create illusions of spaciousness. Therefore, returning to bigger rooms, but fewer of them, can make architectural sense.

One thing is certain about today's houses. Whereas once there were relatively few house types, there are now as many types as life styles, and probably as many life styles as people pursuing them. Roger K. Lewis is a practicing architect and a professor of architecture at the University of Maryland.