380 Mr. E. A. Smith on the Shell-Fauna of 



etiological school brings with it is therefore false ; the true 

 portion of it has long been known as physiology. 



In spite of this it is of great importance to lay especial 

 emphasis upon it ; it was able to render our historic method 

 considerably more profound, and must become an integral 

 part of phylogenetic investigation. To bring it into a 

 mutually exclusive opposition to the historic method, as has 

 been done, is without justification. Without the idea of 

 descent the structure of an animal body cannot be under- 

 stood. One example will suffice. In the whalebone whales 

 teeth appear in the earliest embryonic period. These do not 

 cut the gum, are entirely functionless, and after some time, 

 still in the en)bryo, are completely absorbed. Now how can 

 we succeed in understanding this phenomenon by means of 

 the mechanico-etiological method? Is not our want of a 

 cause satisfied to a certain extent if, on the basis of phylo- 

 genetic investigation, we are able to prove that the germs of 

 these teeth are inherited from ancestors of the whalebone 

 whales, in which the teeth were functional, while in the 

 existing whales, in consequence of an altered mode of life, 

 they are replaced by more practical organs in the shape of the 

 whalebone ? 



In conclusion I would emphasize the fact that I too am 

 convinced that the processes which are termed vital force 

 obey the same laws which dominate the inorganic world. I 

 too behold in the introduction of a vital force, which is to us 

 obscure and mysterious, only an unnecessary addition, and 

 consider the tracing of life to physico-chemical laws, although 

 not as a fact that has been proved, nevertheless as a scientific 

 postulate. 



XLII. — Additions to the Shell-Fauna of the Victoria Nyanza 

 or Lake OuMreive. By Edgar A. Smith. 



Since the publication of my report on the shells of this lake 

 in the ' Annals ' for last August I have discovered that 

 Dr. E. von Martens a month or two previously had described 

 five species from the same locality, namely one species of 

 Limmea, a Phi/sa, and three species of Viviparus. The 

 Fhysa is the species which in his former paper (SB. Gesell. 

 nat. Freund. Berlin, 1879, p. 103) he considered might 

 possibly belong to P. nyassana, Smith. 



