282 GENERATIVE GLANDS. 



probably of the same nature as the provisional renal organ in 

 other Pulmonata. 



Permanent renal organ. According to the most recent ob- 

 server (Rabl, No. 268), whose statements are supported by the 

 sections figured, the permanent renal organ in Gasteropods is 

 developed from a mass of mesoblast cells close to the end of the 

 intestine. This is first carried somewhat to the left side, and 

 then becomes elongated and hollow, and attaches itself to the 

 epiblast on the left side of the anus (fig. 108, r). After the 

 formation of the heart the inner end opens into the pericardium 

 and becomes ciliated, the median part becomes glandular and 

 concrements appear in its lining cells, and the terminal part 

 forms the duct. 



Previous observers have usually derived this organ from the epiblast; 

 according to Rabl this is owing to their having studied too late a stage in the 

 development. 



In Cephalopoda the excretory sacks or organ of Bojanus are 

 apparently differentiations of the mesoblast 1 . At an early stage 

 part of their walls envelops the branchial veins. From this 

 part of the wall the true glandular section of the organ would 

 seem to be formed. The epithelium forming the inner wall of 

 each sack is at an early age very columnar. 



The development of the organ of JBojanus in Lamellibranchiata 

 has been studied by Lankester. He finds that it develops as a 

 paired invagination of the epiblast immediately ventral to the 

 anus. 



Generative glands. The generative glands in Mollusca 

 would appear to be usually developed in the post-larval period, 

 but our knowledge on this subject is extremely scanty. 



In Pteropods Fol believes that he has proved that the hermaphrodite 

 gland originates from two independent formations, one (the testicular) 

 epiblastic in origin, and the other (the ovarian) hypoblastic. 



These views of Fol do not appear to me nearly sufficiently substantiated 

 to be at present accepted. 



The generative glands in Cephalopoda appear to be simple 

 differentiations of the mesoblast. They are at first very closely 



1 I conclude this from Bobretzky's figures. 



