L-STUDY OF THE STRUCTURE OF VARIOUS DEEP-SEA 



MOLLUSCS. 



I. GASTROPODA. 



VOLUTID^. 



1. Gidvillea alahastvina, Watson. Station 147 ; IGOO fathoms. 



A single male specimen, mutilated, the entire visceral sac absent, and probably 

 left in the recess of the shell. Only the cephalic region, the foot, and the anterior 

 margin of the mantle were left, but nothing of the gill. 



I refer, in part, to the description given by Watson,' and can entirely confirm his 

 statement that Guivillea is " a typical Valuta" (PI. I. fig. 1). The foot (e), the pro- 

 boscis (a), the pallial respiratory siphon {h), with its appendage (_;'), the cephalic 

 velum (5), bearing the two tentacles (c), and with the penis {f) at its right extremity, 

 have indeed the same characters as in Valuta. 



The integument, especially on the head and tentacles, is tuljerculated. 



The eyes, said by Watson to be absent, are present {d), but uncoloured, that is, 

 without any pigment. They form two symmetrical projections at the external base of 

 the tentacles, and are distinguished by their size from the integumentary tubercles. 



In fact, these eyes are in structure quite rudimentary, and could not be functional. 



Transverse sections cut across these organs reveal the following structure 

 (PI. I. fig. 2) :- 



The general epithelium of the cephalic region (a) is continued across the ocular 

 prominence, but is more delicate than on the surrounding parts. Below the epithelium 

 the entire optic prominence is covered by a homogeneous structureless layer {h), moie 

 transparent than the surrounding tissues. This la5'er is separated b}^ reticulated 

 connective tissue (c) from the central portion, which forms the principal jsart of the 

 optic prominence. 



This central mass (e) is homogeneous, structureless, staining liut slightly with 

 reagents, and is continued with the same characters into the depth of the cephalic 



1 Zool. Cliall. Exp., part Ivii. p. 201. 



