376 PROCEEDIXGS OF THE ACADEMY OF [April, 



the ectoderm and may have come from that source. The later fate 

 of these cells is unknown, but as they are increasing in size they prob- 

 ably function as important larval oroans. They will here be designated 

 "nephrocysts," for they correspond to cells of similar position and 

 structure described by Trinchese (ISSl) for the larva of Ercolania 

 and other Nudil^ranchs. by whom an excretory function was ascribed 

 them. Older and living material is desirable before making definite 

 statements regarding the nature and function of these apparently 

 similar larval organs of Fiona. 



Numerous investigators have seen and described with various inter- 

 pretations the excretory organs of larval Opisthobranchs. As early as 

 1839 Loven observed the anal kidney in Xudibranch larvae, but did 

 not recognize its function, though indicating that it was probably an 

 undeveloped sexual organ. Likewise Sars (1840) described a similar 

 structure in the veliger of Tritonia, which, together with the large endo- 

 dermal cell which lies near it, he associated in common function with 

 the liver l^dng on the opposite side of the enteron. In ^olis Hke 

 structures were found. Later (1845) he distinguished the vacuolated 

 excretory cell and its neighboring pigmented cells, classing the whole 

 as a reproductive anlage. Reid (1846) observed a like structure in a 

 number of Nudibranchs (Doris, Pohjcera, Doto, etc.), considering it 

 to be probably the heart from contractions which he saw it imdergo. 

 In Vogt's very thorough paper on Actceon, appearing in 1846, the excre- 

 tory organ is somewhat neglected, though his figures indicate its pres- 

 ence. Nordman in the same j-ear described this organ in Tergipes, 

 and referred a reproductive significance to it. Schneider (1858) also 

 found it in Phyllirhoe. iDut assigned no definite fimction. Langerhans 

 (1873), having observed in the living larvae of Doris and Acera cells in 

 the anal region which contained concretions, and from which drops 

 were extruded considered the organ to be of an excretory nature. 

 In 1875 Lankester found similar conditions in Aplysia, and con- 

 sidered the organ to have arisen either from intestinal cells near 

 which it lay or from the ectoderm. 



Trinchese (ISSl) described an ''anal gland for Ercolania wdiich is 

 strongly pigmented and Hes on the right side of the body". This he 

 believed arises from three or four mesodermal cells which acquire 

 pigment and by their division form the organ in question. The same 

 was found in Amphorina, Bergia and Doto, in the last case being paired. 

 In addition to the anal excretory organ, Trinchese also found in the 

 above forms two "rini primive" in the dorsal region under the ecto- 

 derm, one right and the other left. These he described as vesicular, 



