.1888.] 



Presents. 



379 



Seines. When the tail has been broken, however, it is reproduced with 

 an investment of scales arranged in a verticillate manner — a change 

 which shows how small is the real value of a difference which has 

 been deemed by morphologists to be so important a taxonomic character. 

 And here I would venture to make another observation bearing upon 

 taxonomy. The study of the processes of individual development are 

 of course of great importance in determining the nature of the adult 

 animal. Nevertheless that importance may be exaggerated. Raua 

 opisthodon is no less a Bana because it is never a Tadpole. The out- 

 come of the process of development is surely as important as the 

 process itself. Similarly with respect to the evolution of species, the 

 lines of descent are of the highest interest, but if Professor Cope is right 

 as to the diverse ancestry of the oriental and occidental JEquus, then 

 surely its importance may be exaggerated also. The genus Equus is 

 no less one genus for having arrived at maturity along two distinct 

 routes. It seems to me probable that various other natural groups, 

 which are commonly regarded, and I think truly regarded, as natural 

 unities, have become one from various sources. Should this view 

 become generally recognised, it seems to me that the idea of the tree 

 of life will not serve as a basis of a really satisfactory system of classi- 

 fication. Certainly no system could be regarded as satisfactory or 

 natural which placed in widely different groups the two kinds of Horse 

 referred to. 



In concluding, I beg leave to repeat my assertion, that all the teeth 

 of the Ornithorhynchus are unlike any known Sauropsidan teeth, while 

 nevertheless the totality of the structure of Monotremes, and especially 

 the nature of their mammary gland, lend support to the hypothesis 

 that they have become mammals along a different road from that 

 which the higher Mammalia have travelled, and that they gained their 

 teeth by the way, after they had separated off from the main Reptilian 

 stem. This difference of origin nevertheless constitutes in my eyes no 

 reason whatever for not regarding Monotremes and higher Mammals 

 as being all true members of the one class Mammalia. 



Presents, February 16, 1888. 



Transactions. 



Bologna : — Reale Accademia delle Scienze. Memorie. Ser. 4. 



Tomo VII. 4to. Bologna 1886. The Academy. 



Heidelberg : — Universitat. Inaugural-Dissertationen, &c, 1887. 



8vo. and 4to. Heidelberg, Sfc. The University. 



Kiel : — Universitat. Inaugural-Dissertationen, &c, 1887. 8vo. 



and 4to. Kiel. The University. 



London : — Institution of Mechanical Engineers. Proceedings. 



1887. No, 4. 8vo. Loudon. The Institution. 



