ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 345 



by establishing a current of water through certain spaces in the body, 

 and sieving off the food-particles in the current by means of the lopho- 

 phore and its cirri. The cilia on the gill filaments are differentiated 

 in Brachiopods into lateral and frontal cilia in essentially the same 

 way and with the same functions as in Lamellibranchs, etc. The main 

 current through the mantle-cavity is produced chiefly by rows of lateral 

 cilia on the cirri. The mantle-cavity in Brachiopods is divided physio- 

 logically into two compartments, corresponding to the bilateral symmetry 

 of the lophophoral spirals. In some forms it is also divided morpho- 

 logically either by septa or by bifurcation of the whole shell. Food 

 collection is effected mainly by the frontal cilia on the gill-filaments, but 

 tracts of cilia on the filamental side of the lophophore assist in capturing 

 food-particles. For the capture of food-particles mucus is secreted on 

 the frontal epithelium, at the bases of the gill-filaments and on the 

 body of the lophophore. Some of the characters of the shells of many 

 fossil and recent Brachiopods can be partially explained in relation to 

 the physiological subdivision of the mantle-cavity. 



The cephalic gills of cryptocephalous Polychajtes have current- 

 producing lateral cilia and frontal food-collecting cilia essentially similar 

 to those of the other groups under discussion. Thus the ciliary 

 mechanisms on the gills of many Gastropods, most Lamellibranchs, 

 Amphioxus, Ascidians, Brachiopods, and the cryptocephalous Polychastes 

 are essentially similar, and in the three groups to which these animals 

 belong the same mechanism, and similar gill-filament supports have 

 arisen independently to meet similar requirements. An endostyle 

 present at the base of the gill in Crepidula, Cahjptrsea, and probably in 

 Capulus, shows a remarkable resemblance to that of Ascidians and 

 Amphioxus and serves the same purpose. The adaptations in Brachiopods 

 and Lamellibranchs to the process of feeding are compared, and the 

 author suggests that the present decadent condition of the former group 

 is due to the absence of that consolidation of the gill, and correlated 

 modification of the mantle, which appear to have conduced to the present 

 relatively flourishing condition of the Lamellibranchs. 



INVERTEBRATA. 



Mollusca. 

 7« Gastropoda. 



Structure of Helix barbara.* — T. Rzymowska has made an 

 anatomical and histological study of this small snail, which is common 

 on the sea-holly on the shores of the Mediterranean and on the European 

 Atlantic coast. He deals in particular with the nervous system, and 

 contributes some interesting data in regard to the dimensions of the 

 nerve-cells at different ages. The nerve-cells increase in size as the 

 animal grows older. Rzymowska deals also with the reproductive 

 system, which closely resembles that of Helix pomatia, and calls attention 

 to the prismatic cells of the prostatic part of the oviduct, the calcareous 



* Rev. Suisse Zool., xxii. (1914) No. 10, pp. 277-319 (2 pis.). 

 Aug. 19th, 1914 2 a 



