Gametogenesis in Cestodes, 
427 
There is of course the possibility that the attaclinient of the sperms here is 
secondary and not dne to their origin from such masses. Tliey have been 
f ound however in youngtestes, where sperm formation was actually procees- 
ing, and the sperms themselves wereevidentlyimmaturejudgedby their size. 
But perhaps the strongest evidence against the direct participation 
of any nucleus in the formation of the sperm is that shown in figs. 16, 17, 
21, 26, 28, 34, 35 and 40, which are camera drawings of living material 
from Rhyncobothrium. In these drawings are shown numerous instances 
of two and even three sperms attached to uninucleate portions of the 
cytophore, representing second spermatocytes or spermatids. That these 
are developing sperms, is shown by their length, which is very much less, 
in many cases at least, than that of the mature elements. Generally these 
developing sperms are no-motile, linder the conditions of observation at 
least ; but in one case (fig. 36) I observed several developing sperms which 
were clearly motile. Obviously if two or more sperms are attached to the 
territory of one nucleus, that nucleus cannot directly contribute to all 
of them ; tho it niay do so indirectly thru its influence upon the cytoplasni 
where these sperms are developing or thru the contribution of chromidia 
to each. It is only in Rhyncobothrium that I have observed this develop- 
ment of sperms in groups. In other species (Taenia pisiformis and teniae- 
formis and Dipylidium caninum) they develop one to a “cell” and in 
Rhyncobothrium the latter is frequently, if not usually the case. Here 
however repeated observation shows that there is no constancy in the 
number of sperms arising from a single “cell”, and hence that the nucleus 
does not form part of the sperm in the ordinary sense ät least. 
But how bring these observations into line with those which I have 
occasionally made in fixed material of elongating nuclei which are appa- 
rently giving rise to sperms? It is not, of course, certain that they actually 
are so doing, but the pictures certainly indicate it. I have seen one 
case in living material which is somewhat similar to these. This is shown 
in fig. 22 which is a free hand sketch of a sperm attached to a cytophore, 
with the proximal end of the former forking into two more or less parallel 
lines. In the majority of cases however in both fresh and fixed material 
the sperms arise as solid structures with no indication of any nuclear 
elongation in their development. It is possible that instances of such 
elongation, which are comparatively infrequent, have not occurred, or 
have been overlooked by me in the fresh material which I have studied. 
The question is in any event of comparatively little consequence, since 
the secondary nuclei of the cytophores probably arise from the skein 
fragments, from which in the majority of cases the sperms also are formed. 
