586 SUMMARY OF CURRENT RESEARCHES RELATING TO 



several naturalists had confounded the appendages of certain molluscs 

 with the true Phamicurus ; as to the hepatic trunk spoken of by Bergh, 

 it is not the dendroccelous digestive tube of Phoenieurus for that has no 

 resemblance to a hepatic appendage ; the so-called mouth is really 

 the external circulatory orifice ; this question is entered into in 

 great detail. At the end of a number of arguments forcibly put M. de 

 Lacaze-Duthiers pertinently asks what can bo the use to the Tethys 

 of such large appendages which fall off so easily ? 



Pericardial Gland of Lamellibranchs and Gastropods.* — Prof. 

 C. Grobben, who has already shown that the so-called branchio- 

 cardiac appendage of the Cephalopoda is a glandular structure, now 

 extends his observation to other classes of the Mollusca. In the 

 Lamellibranchiata the pericardial gland has either the form of 

 glandular lobes or of caeca, which are developed from the peri- 

 cardiac epithelium, and lie in the anterior angle of the pericardiac 

 space. The lobes are found in Area, Mytilus, Pecten, and Ostrea ; 

 the lobes in Unio, Venus, and Scrobicularia, but they differ con- 

 siderably in their grade of development. The epithelial cells which 

 form the gland contain concretions of various forms and sizes. 

 Among Gastropods a similar organ is to be observed in Fissurella, 

 Parmophorus, Ealiotis, Turbo, and Trochus. 



The function of the gland appears to be excretory, and to be 

 allied to the renal ; the products probably escape into the kidney, 

 whither they are driven by its ciliated infundibula. The glands 

 appear to have a general homology with those already described in 

 Cephalopods ; their presence in the last-mentioned group leads the 

 author to believe that the Cephalopoda represent a branch of the 

 molluscan phylum which very early became independent of the rest. 



Pedal Gland and Aquiferous Pores in Lamellibranchs.f — Dr. 

 T. Barrois has studied in sixty species the glands of the foot and the 

 aquiferous pores of Lamellibranchs ; the differences which obtain in 

 the different families are described, and the conclusion is arrived at 

 that the byssus is peculiar to the group, and is secreted by glands 

 which are homologous with the pedal glands of Gastropods ; various 

 stages of degradation are to be seen in various families. The ex- 

 amination of the intercellular canals and aquiferous pores, which are 

 in some forms completely wanting, has shown that the so-called 

 aquiferous pores are really the orifices of the byssogenous glands, and 

 that there is no direct communication between the circulatory appa- 

 ratus and the exterior ; there is, in fact, no mixture of blood and water. 



Eyes of Pecten. J — Eeferring to Hickson's theory that the " eye " 

 on the mantle of Pecten serves to warn the animal of the ebbing tide, 

 by reason of its being affected by the growing intensity of the light, 

 Prof. B. Sharp has reason to think that this " eye " is an organ not 

 for admission but for emission of light ; that is, that it is the organ 

 whence the phosphorescence observed in this mollusc is derived. 



* Zool. Anzeig., ix. (1886) pp. 369-71. 



f Pp. 170, 8 pis. 4to, Lille, 18S5. Cf. Journ. de Microgr., x. (1886) pp. 93-5. 



% Proc. Acad. Nat. Sci. Philad., 1886, pp. 61-2. 



