376 PROCEEDINGS 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 organs. They will here be designated 
“nephrocysts,” for they correspond to cells of similar position and 
structure described by Trinchese (1881) for the larva of Ercolania 
and other Nudibranchs, 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 Lovén observed the anal kidney in Nudibranch larve, 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 lying on the opposite side of the enteron. In olis like 
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, Polycera, Doto, etc.), considering it 
to be probably the heart from contractions which he saw it undergo. 
In Vogt’s very thorough paper on Actwon, appearing in 1846, the excre- 
tory organ is somewhat neglected, though his figures indicate its pres- 
ence. Nordman in the same year described this organ in Tergipes, 
and referred a reproductive significance to it. Schneider (1858) also 
found it in Phyllirhée, but assigned no definite function. Langerhans 
(1873), having observed in the living larvee 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 (1881) described an “anal gland for Hrcolania which is 
strongly pigmented and lies 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, 
