342 NATURAL SCIENCE [May 



into orders," one would have expected more direct evidence, more 

 illustration, and more discussion of apparent difficulties, such as the 

 abnormalities (for so I am content to regard them) met with in 

 Apiocrinus, or the exactly opposite view maintained by some pre- 

 ceding writers concerning some of the genera mentioned. 



Accepting the character as valid in the absence of actual disproof 

 of its universality, we see that it enables a clear separation to be 

 made between such a form as Sagenocrinus and certain Camerata, 

 between Pycnosaccvs and the Botryocrinidae, between Millericrinvs 

 and Antedon on the one hand, and the Pentacrinidae on the other. 

 A proximale occurs in the former in each ease, but not in the latter. 

 But it does not follow from this that the presence of a proximale 

 indicates genetic affinity. There can, it is true, be little doubt that 

 all the Palaeozoic genera placed by "Wachsmuth and Springer in their 

 Order Articulata are allied ; they can scarcely be separated even 

 into genera. But it is by no means clear that they are the 

 ancestors of the Neozoic genera placed in the same Order. 



The Neozoic Articulata are distinguished from the Palaeozoic by 

 the possession of ' pinnules,' which are defined by our authors as 

 " small lateral appendages, given off alternately from opposite sides of 

 the arms," to wliich should be added, that tliey have the same anato- 

 mical structure as arm-branches, but that they do not branch them- 

 selves, that their alternating arrangement is regular, and that when 

 present the maturation of the generative products takes place only 

 in them. I have long urged the view, in which I still firmly 

 believe, that pinnules are derived from arm-branches, of which they 

 are, " as happily expressed by Carpenter, repetitions on a small 

 scale " (Wachsmuth and Springer). I am astounded to find that, in 

 the opinion of the learned American writers, my " views respecting 

 the pinnules are rather peculiar " ; I fail to see any meaning in the 

 argument that my " explanation is not satisfactory, as it would 

 indicate that the smaller appendages are derived from the larger 

 ones " ; as for their belief that " every species of Botryocrinus [the 

 genus on whose evolution I based my theory] has armlets, and that 

 pinnules are not represented in any of them," I can only say that 

 it can never be shared by anyone that has seen the type-specimen of 

 Botryocrinus pinmilatus. 



Our authors nowhere attempt to explain the origin of pinnules, 

 so we are left to infer that they regard them either as independent 

 developments, somewhat sudden in their first appearance, or as 

 structures handed down from some Cystid ancestry. That they 

 regard the possession of pinnules as a strong distinctive character, is 

 shown by their further criticism of me on p. 161, where they say 

 that I " cannot do " a great many tilings which I have done. When, 

 therefore, they separate their so-called Articulata into the non- 



