346 SUMMARY OF CURRENT RESEARCHES RELATING TO 



and mucous glands of the infra-prostatic part of the oviduct, the two 

 kinds of glandular cells in the prostate covering the external margin of 

 the sperm-duct, and other details. 



Alleged Nematocysts of Pleurophyllidiae.* — L. Cuenot refers to 

 the fact that the supposed nematocysts of JEolids are due to the 

 Ccelenterates which the molluscs eat. In Pleurophyllidia, however, 

 there are dorsal sacs containing filaments which are expelled when the 

 Nudibranch is violently excited, and these sacs have no communication 

 with the hepatic ramifications. Moreover, the Nudibranchs in question 

 seem to feed on organic particles and diatoms, not on Ccelentera as 

 Solids do. The sacs are peculiar glands, and the elongated (possibly 

 offensive) filaments they form have nothing to do with nematocysts. 

 The sacs may be compared to the sub-epidermic " phylacoblasts " described 

 by Andre in Hyalinia, but it is a remote resemblance. The sacs of 

 Pleurophyllia are epidermic invaginations ; the cytoplasm of the com- 

 ponent cells is turned into a filament ; the sac becomes a pouch full of 

 filaments ; after expulsion occurs the sac disappears, its place is invaded 

 by connective-tissue, and young sacs are formed. 



5. Lamellibranchiata. 



Structure of Bivalve Shell. f— H. Karny has investigated the 

 structure and composition of the calcareous shell in Aviculidae and 

 Unionidae. It consists of a prismatic and a nacreous layer. The pris- 

 matic layer of Pinna consists of calcite ; each prism is comparable to 

 single crystal, with its axis at right angles to the surface of the shell. 

 In Aviculidae the prismatic layer is also of calcite, but there is no radial 

 structure. Each prism is made up of pieces, which are not regularly 

 arranged in relation to the surface. The first condition may be called 

 orthoprismatic, the second klinoprismatic. In Unionidae the prisms 

 consist of aragonite, and the structure is " radio-sphaerolithic," only the 

 middle lines of the median portions of the prisms being at right angles 

 to the surface. The nacreous layer also consists of aragonite. Its 

 structure is described in detail. 



Structure of Kidney of Anodonta.J — Wilhelm Fernau publishes 

 the first — the morphological — part of a study of the kidney of Ano- 

 donta cellensis Schrot. He finds that the kidney — the so-called organ 

 of Bojanus — is a paired nephridium. Each nephridial tube is con- 

 nected by a specially differentiated canal, the nephridial funnel, with 

 the pericardium, and thence it extends as a much folded sac (proximal 

 loop) directly towards the anus as far as the posterior adductor ; there 

 it turns, at first in winding coils and then straight, dorsally over the sac, 

 as the nephridial duct (distal loop), towards the mouth, and opens into 

 the mantle cavity by a special ureter quite close to the nephridial funnel. 

 The two ducts communicate with one another and surround the sacs 



* Arch. Zool. Exper.,liv. (1914) Notes efc Revue, No. 1, pp. 14-18 (3 figs.), 

 t SB. Akad. wiss. Wien. Math. Nat. Klasse, cxxii. (1913) pp. 207-59. 

 t Zeitschr. wiss. Zool., ex. (1914) pp. 253-301 (24 figs.). 



