224 PKOCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



they are primitive, and indicative of stages in phylogeny. His action 

 imposes on us the necessity for paying foremost attention to those 

 characters in mollusca which may he of larval significance, and 

 especially to such as both living and fossil forms may present. 



Duiing the last few years, much interest has attached to a con- 

 sensus of opinion among specialists that the Phyllopoda lie near the 

 base of the Crustacean series, and to the growing idea that they may 

 be closely related to the Trilobites. Beecher, from the study of speci- 

 mens of Triarthrus Becki, in which the appendages are preserved, has 

 substantiated this; and shown us,' what to my mind is incomparably 

 more important, that in the Trilobite, as in the Nauplius, the first pair 

 of appendages are prostomial, antenniform, and uuiramous, and that the 

 two pairs which follow are peristomial and biramous. When we con- 

 sider further that the Trilobite in its general characters most nearly 

 combines those of Nauplius and the Phyllopod, which is develop- 

 mentally a sort of expansion of the Nauplius ; that segmentation and 

 ' cephalization ' of the arthropod body are secondary processes, which 

 can be accounted for by growth and development ; that many of our 

 dec:ipods themselves pass through a Nauplius stage ; and that the 

 ' median eye ' of the Nauplius has been found attached to the brain, 

 altogether hidden beneath the exoskeleton, in adults of even the 

 more familiar decapods'-; our interest in the larva and in all questions 

 of Crustacean phylogeny is heightened, in a manner impossible by 

 any but the comparative morphological method. 



Tasmania has recently yielded us,^ in the Anaspides of Thomson, an 

 annectant crustacean type ; and within the last three mouths Caiman, 

 uiinutely comparing this with the Palieozoic pod-shrimps so long 

 anomalous, has left little room for doubting* that it carries the decapod 

 type a stage lower than the lowest living schizopod. 



As affecting our views of the phylogeny of the Crustacea, the 

 observations which I have here brought together appear to me to 

 liave achieved a far-reaching result, impossible from the exclusive 

 study of either the living or the extinct : and when we consider 

 that specialization of recent years has given us a school of zoologists 

 brought up in little short of contempt for paloeontology, it behoves 

 us to take the lesson to heart. The observations do more; they 

 demand of us a more careful study of palasontology, as a branch of 

 morphology — especially as it may hear upon larval characters, 

 and such particularly as may be retained by the adult in a con- 

 dition capable of fossilization. They show us that we are wasting 

 too much time and energy on speculation as to what may have 

 happened during the evolution of living organisms, to the 

 ignoring of what has happened ; for, whatever may have been the 

 changes, they must have left their impress in the rocks. I would 



1 C. E. Beecher, Amer. Jouni. Sci., ser. IV, vol. i, p. 251. Cf. also Amer. 



Geol., vol. XV, p. 93. 



2 Cf. C. Bumpiis, Zool. Aiiz., Bd. xvii, p. 176. 



3 G. M. Thomsuu, Traus. Liiiu. Soc. (Zool.), ser. II, vol. vi, p. 3. 

 < \V. T. Caliuau, Traus. Roy. Soc. Eiliub., vol. xxxviii, p. 7«7. 



