222 PHOLADID^E. 



has been mentioned under the heads of the organs I have 

 described, except those of the ovary, which will be noticed 

 hereafter. These animals, like all the Bivalves, are strict 

 hermaphrodites. The ovarium is a white glandular body 

 entwined with the liver, but as it approaches the pericardium 

 it becomes a distinct mass ; and, what is unusual at this time 

 of the year (20th January), in several of the ovaria the contents 

 had begun to assume the appearance of ova; but with the 

 utmost power of the microscope I could not perceive any 

 trace of the membranous pyriform bodies containing a fluid 

 which I have observed in the genial months in many of the 

 ovaries of the strict hermaphrodite Bivalves and Gastero- 

 poda, which I consider to be the male influences ; nor could 

 I discover any other organ that had the slightest pretension 

 to be regarded of a similar nature. I failed to verify the 

 oviduct, but from the position of the ovarium I have little 

 doubt that it passes at and under that portion of the peri- 

 toneal cavity which contains the terminus of the ovary, into 

 the anal compartment of the mantellar tube, about 1^ inch 

 above the siphon, and that the ova are there discharged. 

 I do not think the branchiae in this species serve as re- 

 ceptacles for the ova ; their structure is not calculated for 

 such purpose. 



I will now make a few observations on the camerated 

 structure of the posterior part of the protective tube, which 

 has caused malacologists much speculation on its uses ; some, 

 myself amongst others, thought the laminar spaces might 

 be to protect the pulli for a time until ultimate exclusion. 



These ideas were dispelled by the discovery of the fixture of 

 the posterior part of the animal by the strong oval muscles 

 springing from the sphincter, which induced me to examine 

 this portion of the tube with care, and in a fine full-grown 

 specimen I discovered the principal object, if not the precise 

 animal ceconomy, of the laminae. I perceived in the centre of 

 each plate a decided muscular impression, which, on compa- 

 rison with the last-formed one of the sphincter muscle, proved 

 to be identical in shape ; this fact made it evident, that the 

 animal, either when full-grown, or when growing, if its longi- 



