82 n. J. Fr.EiiRK. 



lobe (s. v.. L.), but opinion varies as to a pericardial pore of the 

 left kidney^ the latest statement being that of Mr. E. S. 

 Goodrich (11)^ who makes certain he has found it. 



Mr. Martin Woodward has recently published a valuable 

 account (14) of Pleurotomaria Beyrichii^ in which he 

 says that the right (7 r) and left (7 l) kidneys of that animal 

 are in many respects comparable with the corresponding parts 

 in Haliotis. The efferent duct of the right kidney (7 R to 2) 

 is prolonged forwards^ and has thick glandular walls in the 

 female^ so that it is practically an oviduct. Woodward 

 found a pericardial opening and canal (4) for the left kidney 

 but not for the rights a result which^ if confirmed, makes 

 Pleurotomaria an exception to the general rule. 



The most primitive type of kidney in Diotocards is^ how- 

 ever^ that of Cemoria described by Haller (9). Here both 

 kidneys are well developed and functional, each communis 

 eating with the pericardium (vifi 4 and 5), and each receiving 

 genital products from the gonad of its side. If this type is 

 truly primitive we can, as Haller has said, derive from it the 

 excretory organs of Pleurotomaria, Haliotis, and the Trochidoc, 

 from which series the Docoglossa and the Fissurellida) would 

 be fairly early offshoots. Throughout, the left kidney and 

 the left gonad degenerate, whilst the right kidney becomes 

 both the functional excretory organ and the exit channel for 

 the sex products. The right kidney retains, in most forms, 

 its pericardial pore. 



Perhaps the most marked contrast between the Diotocards 

 and their Monotocard descendants is the presence of 

 numerous accessory genital organs in the latter and their 

 complete absence from the former group. In the latter, also, 

 the reproductive and excretory systems are entirely separate. 

 We must therefore seek out hints of the coming change 

 among the ancestral forms. 



Mr. Woodward has shown that the excretory duct of the 

 rio-ht kidney of Pleurotomaria is practically transformed, in 

 tlic female, into an oviduct (vide fig. 2). 



In Haliotis the large anterior lobe (a. l., fig. 4) of the right 



