18 SUMMARY OF CURRENT RESEARCHES RELATING TO 



uterinus which here and in related Doriidae bears three seminal vesicles. 

 Their exact significance has not been made out. 



Genitalia of Lymnea.* — F. C. Baker describes the genital organs 

 of Lymncea stagnalis appresa Say, and other American forms — 9 species 

 and 2 varieties. There are noteworthy differences in the length of the 

 penis in relation to the penis sac, in the penis retractor muscles, in the 

 colour especially of the receptaculum, and so on. The characters aid 

 greatly in the separation of the species, but do not seem to aid materially 

 in the establishment of higher groups. 



5. Lamellibranohiata. 



Parasitism of Anodonta Larvse.f — V. Faussek gives a full account, 

 in Russian, of the changes which befall the Glochidia of Anodonta 

 after they become parasitic on the fins or gills of fishes or Amphibians. 

 Among the hosts infected he deals with Alburnus lucidus, Perea 

 Jluviatilis, Osmerus eperlanus, Carassius auratus, tadpoles of frog, Siredon 

 pisciformis. 



Oysters of Senegambia.ij: — A. T. de Rochebrune has investigated 

 the question of the fossil oysters of Senegal, and concludes that they 

 are not Etheridae, as has been alleged. The Etheridae have not lived 

 and cannot live in the Senegal and its affluents below 110 kilometres 

 from the mouth of the river, on account of the saltness of the water. 

 The oysters are of Quaternary age like those of Gambia. Lamarck's 

 Oryphcea angulata is simply a deformed individual, and cannot be used 

 for the oyster of Portugal. The name angulata must give place to 

 G. rostralis Lamarck. 



Ligamentary Structures in Bivalves.§ — R. Anthony has followed 

 the development of the shell from its beginning to the adult condition 

 in JEtheria caillaudi Feruss., and has demonstrated the progress of the 

 pseudo-plicature and the formation of the ligamentary crest which 

 follows from it, as well as the consequent modifications of the ligament. 

 The general conclusion is that the development of these structures in 

 the Acephalae is analogous to that in the iEtheriidas — that, in fact, there 

 is here an example of convergence. 



R. Anthony || has made an elaborate study of those " pleurothetic " 

 bivalves, i.e. those whose sagittal plane (bucco-ventral-ano-dorsal) is 

 parallel to the plane on which they rest. Those whose sagittal plane is 

 perpendicular to the plane on which they rest are called " euthetic." 

 The pleurothetic Dimyaria are Dimyidas, Chamidas, Myochamidse, 

 Chamostreidas, iEtheriidas, Rudistae, and Chondrodontidae. He shows 

 what consequences the pleurothetic position may be said to have, e.g. a 

 coronal symmetry takes the place of the primary sagittal symmetry ; the 

 form tends to become rounded ; the siphonal and pedal apparatus tends to 

 be reduced. 



* Amer. Naturalist, xxxix. (1905) pp. 665-79 (11 figs.). 



t Mem. Acad. Imp. Sci. St. Petersbourg, xiii. (1903, received 1905) pp. 1-141 

 <8 pis.). 



% Mem. Soc. Zool. de France, xvii. (1904) pp. 191-201. 



§ Comptes Rendus, cxl. (1905) pp. 948-50. 



H Arm. Sci. Nat., ser. 9, i. (1905) pp. 165-397 (3 pis., 57 figs.) 



