766 RECORD OF CURRENT RESEARCHES RELATING TO 



a canal wliicli ends in a larger cavity, plicated and lined witii glands ; 

 these structures represent the byssal apparatus of those Mollusca 

 which possess it. The canal represents the open groove of Cardium 

 edule and the half-closed groove of Pecten maximus ; but these species 

 have also certain glands situated in it, which have no homologues in 

 Tellina ; its terminal glands, however, represent the byssal glands. 



Scrobicularia piperata differs in the arrangement of these parts 

 from Tellina only by the inferior length of its canal. 



In Donax anatinum, the opening is also posteriorly placed ; the 

 canal is short and leads into a cavity whose walls are covered with 

 cylindrical epithelium ; no gland cells occur, they are replaced by an 

 extremely dense mass of connective tissue which is not stained by 

 reagents and shows no trace of gland cells. This is the furthest 

 stage of degradation reached by the apparatus of the byssus in this 

 family. 



Thus in these forms the opening of the duct is transferred from 

 front to back, the groove is replaced by a canal, the glands of the 

 groove are entirely lost, and in one of the species [Donax) the byssal 

 glands are aborted. 



Anatomy of the Bullidea.* — M. Vayssiere is principally occupied 

 in this essay with the description of that imperfectly known form 

 Gasteropteron Meckelii ; but the difficult family to which this species 

 belongs presents several points in which our knowledge is very far 

 from being satisfactory ; its representatives differ considerably from 

 one another in their external characters, and some among them are 

 almost completely deprived of any shell. Members of the group may, 

 however, be recognized by the facts that the dorsal region of their 

 body is divided into four parts, and that both labial and dorsal 

 tentacles are altogether absent. 



It will not be necessary to follow our author through the histori- 

 cal chapter in his paper ; coming at once to the genus Gasteropteron, 

 we find that in it there are at any rate no more than two described 

 species, G. Meckelii of Kosse, and the very slightly different G. sinense 

 of A. Adams. The former species, with which alone the French 

 naturalist now concerns himself, is from 20 to 24 mm. long, and from 

 25 to 30 mm. broad ; the body proper is even much smaller than 

 this. 



In its general appearance it has no slight resemblance to a 

 Pteropod, and in that order the earlier naturalists were content to 

 place it ; the shell is somewhat difficult to detect, and was never 

 observed till 1860, when Krohn signalized its appearance ; it is only 

 4-5 tenths of a millimetre in size, is " nautiliform," hyaline, and very 

 translucent, so that it has a very striking resemblance to that of a 

 Carinaria ; it is found in the hepatic organ, is situated near to the 

 anus, although somewhat behind this orifice, and a little on the 

 right side. 



Digestive System.— This portion of the animal is exceedingly 

 simple ; the oral orifice is situated in the centre of a slight depression, 

 and just in front of the anterior portion of the foot ; on either side 

 * ' Ann. Sci. Nat.,' ix. (1880), Art. 1. 



