counted for, and the process of the development of the orders and sundry lesser groups of the Vertebrate kingdom indicated.24 (1870, in 1887, p. 143)

Alpheus Hyatt and Universal Acceleration

Alpheus Hyatt learned the principle of recapitulation from his teacher Louis Agassiz; thereby, he continued an intellectual lineage extending back directly to Oken.

I must have got directly from him, subsequently to 1858, the principles of this branch of research, and through this and the abundant materials furnished by the collections he had purchased and placed so freely at my disposal, I soon began to find that the correlations of the epembryonic stages and their use in studying the natural affinities of animals were practically an infinite field for work and discovery . . . The so-called Haeckelian "law of biogenesis" is really Agassiz's law of embryological recapitulation restated in the terms of evolution. (Hyatt, 1897, p. 216)

Alpheus Hyatt, Boston's celebrated invertebrate paleontologist, concentrated his work on cephalopods and wrote two major evolutionary treatises: Genesis of the Arietidae (1889) and "Phylogeny of an Acquired Characteristic" (1893). His publications ranged widely and included a monograph of the freshwater snails of Steinheim (1880); death interrupted his work on the famous Hawaiian tree snails.

His views on recapitulation run in remarkable parallel to those of Cope. They both developed the law of acceleration in 1866 (Cope, 1866, p. 398; Hyatt, 1866, p. 203). Both altered their concept of progressive evolution from a belief in foreordained stages to a conviction that animals acquire new characters by their own activity. Although they did not publish jointly, each lavished praise upon the other and happily shared credit for the major concepts of recapitulation.25

An epitome of the major argument in Hyatt's most famous treatise (1893) displays his manner of thinking and working. Nautiloids begin ontogeny with a straight shell. At a very small size, the shell begins to coil loosely; the whorls are not yet in contact. Finally, as the coil tightens, the whorls come into contact and remain in contact throughout growth (Fig. 8). A groove, running along the inside (dorsal) surface of each whorl, is called the impressed zone. In phylogeny, this zone arose mechanically from pressure exerted by contact of the inner surface with the outer keeled edge of the preceding whorl. This acquired character was then inherited and accelerated to earlier and earlier stages. Finally, the impressed zone appeared on the earliest, loosely coiled and uncoiled portions of the shell. It cannot have been imposed there by direct pressure since there is no contact