This review has only covered a limited portion of a very broad topic, and I apologize for any other important aspects I have left out. However, I hope I have conveyed an adequate impression of what morphology is all about and how it has helped in our understanding of galaxies. In my opinion, the best approach to morphology is to view it as an imprecise science which serves as a means to an end but which is not an end in itself. Morphology cannot generally stand alone and, as pointed out by Dressler (1980a), is not a suitable substitute for physics. However, as pointed out by Kormendy (1979) and Dressler (1980a), morphology can suggest powerful avenues for further research. A purely physical classification is not likely to replace morphological classification for many years.
To answer the question as to where morphology has led us in understanding galaxies, I think it has given us insights by causing us to focus our attention on specific types of objects. Spiral galaxies were the subject of much research in the 1960's and 1970's, while the 1980's could be called the decade of the elliptical galaxies. For the various classes of galaxies, we have sought to measure more basic physical parameters, such as optical and infrared luminosities, colors, surface brightness distributions, HI contents and distributions, CO distributions, rotation curves and mass distributions, diameters and intrinsic flattenings, velocity dispersions, radio continuum fluxes and distributions and kinematics and dynamics of internal structures, and we have used these physical measurements to piece together what determines morphology and what role the invisible parts of galaxies may play in the overall dynamics. The beauty of morphology is that there are not purely random correlations between many of these parameters and galaxy structure, as is highlighted by the smooth variations of some quantities with position along the Hubble Sequence (see Whitmore, 1984 and Watanabe et al., 1985 for recent applications of principal component analysis). Thus, morphological classification in conjunction with physical measurement has been an important tool in extragalactic astronomy.
The advent of CCD technology, the high quality sky surveys, and the Hubble Space Telescope suggest to me that there is an exciting future for morphological studies. Considering the extensive interest in early-type galaxies among the attendees at this conference, a homogeneous imaging survey of all real or suspected E, S0 galaxies in a well-defined sample (e.g., Sadler, 1984) may be more practical than ever before and may help to alleviate some of the uncertainty in interpreting HI and other properties of these objects. Even more exciting are the prospects from HST, which at some point should allow the study of morphology in very distant galaxies where we may be able to see evidence for secular evolution. This will be important not only for star formation histories, but also for bars, rings, spiral structure, and the distribution of types. For nearer galaxies, CCD's are already providing excellent image material for morphology studies. The efficiency and linearity of these detectors makes it possible to image more galaxies on a large scale and to a deeper limiting surface brightness than ever before. With such high quality images becoming available, more and more attention will be paid to finer details of morphology as theories and observations get more sophisticated. Finally, future large surveys will probably involve computer classification from digital images to a great extent (see Thonnat, 1989; and Delfini, Accomazzi, Kurtz, and Mussio, this conference).