Seminal Products in Limpets. By W. H. Dall. 195 
Patellide and by a process of straining through the glandular mass 
in the Acmeide. Whatever their office, it can hardly be of 
fundamental importance, or they would not be so frequently found 
in an abortive condition. Whether in some cases they may be 
indirectly in communication with the renal sac is of little conse- 
quence, as, in the paper alluded to, I have shown that in some 
genera the pericardium is so situated that there can hardly be any 
such communication, and in so homogeneous a group as the limpets 
it is unlikely that such an anatomical character, if important, 
should be inconstant. 
Moreover, through the intricate channels alluded to, the ova 
which are of considerable size could hardly be propelled without 
some special muscular arrangement which does not seem to be 
present in any case examined. Anxious to set at rest a question 
of so much interest, and which for so many years had puzzled 
anatomists, I have lost no opportunity of dissecting animals of this 
group, especially the large species in which the characters might 
be supposed to be more evident. The opacity of the shell and the 
impossibility of getting at even the external orifices of the viscera 
without destroying the life of the individual, proved effectual 
obstacles to the study of these functions in the living animal. 
While in the field, from 1871 to 1874 inclusive, I made dissections 
of many hundreds of acmzeas with no definite result, except that of 
finding that the sexual products appeared ripe in only a small 
portion of the ovary at any one time, and in the acmeas the 
portion most usually in that condition was the extreme right-hand 
part of the anterior end, immediately below the floor of the larger 
renal sac. No oviduct or opening was in any case demonstrated. 
Somewhat discouraged by repeated failure, on leaving the field- 
work in which I had been engaged, the matter was deferred until 
a better opportunity should arise. Some time since, a large number 
of specimens of the giant limpet of Central America, Ancistromesus 
Mewicanus, were obtained by the Museum of Comparative Zoology 
from the naturalists of the ‘Hassler’ expedition. By the courtesy 
of Professor Alex. Agassiz a number of these were turned over to 
me for dissection. 
In this species the right supra-renal sac is quite large, covering 
the entire superior surface of the animal between the muscular 
attachments.. The viscera are coiled below it in the usual manner, 
except that in ripe individuals the upper outer edge of the ovary 
or testis extends rather more beyond the peripheral coil of the 
intestine than in most species. A section then discloses the mem- 
branes in the following order from above. 
First, the external delicate layer of the mantle covering every- 
thing else, and very intimately bound together by tough connective 
tissue, with 
