HYATT. — ORGANIC CYCLES. 213 



would have placed him iu the history of science on the same line with 

 Lamarck and Darwin. 



He states in fourth lecture, p. 26, as follows : " The results thus far 

 obtained in the lectures which I have delivered can be expressed as 

 follows. There is a gradation of type in the class of Echiuoderms, and 

 indeed in every class of the animal kingdom, which, in its general out- 

 lines, can be satisfactorily ascertained by anatomical investigation ; but it 

 is possible to arrive at a more precise illustration of this gradation by 

 embryological data. The gradation of structure in the animal kingdom 

 does not only agi-ee with the general outlines of the embryonic changes. 

 The most special comparison of these metamorphoses with full-grown 

 animals of the same type leads to the fullest agreement between both, 

 and hence to the establishment of a more definite progressive series than 

 can be obtained by the investigation of the internal structure. These 

 phases of the individual development are the new foundations upon 

 which I intend to rebuild the system of zoology. These metamorphoses 

 correspond, indeed, in a double sense, to the natural series established in 

 the animal kingdom : first, by the correspondence of the external forms, 

 and secondly, by the successive changes of structure, so that we are here 

 guided by the double evidence upon which the progress in zoology has, 

 up to this time, generally been based. 



"Their natural series again correspond with the order of succession of 

 animals in former geological ages, so that it is equally as true to say that 

 the oldest animal^ of any class correspond to their lower types in the 

 present day as to institute a comparison with the embryonic changes, and 

 to say that the most ancient animals correspond with the earlier stages of 

 growth of the types which live in the present period. In whatever point 

 of view we consider the animal kingdom, we find its natural series agree 

 with each other ; its embryonic phases of growth correspond to its order 

 of succession in time, and its structural gradation, both to the embryonic 

 development and the geological succession, corresponds to its structure ; 

 and if the investigations had been sufficiently matured upon this point, I 

 might add that all these series agree also in a general way with the geo- 

 graphical distribution of animals upon the surface of our globe, but this is 

 a point upon which I am not yet prepared to give full and satisfactory 

 evidence. So much for the views referring to embryology in its bearing 

 upon zoological classification." 



And again on page 27 : — 



" However, another step had to be made to show a real agreement 

 between the earlier types of animals and the gradual development of the 



