ME. P. H. GOSSE ON THE DKECIOTJS CIIAEACTEE OE THE EOTIEEEA. 323 
whatever it be, no semblance of such viscera is to be traced in A. priodonta, or in any 
other male that has come under my observation. 
35. Another curious peculiarity is the dissimilarity that always subsists between the 
sexes. In AsplancJina and Hydatina the resemblance is at its highest point : in every other 
instance observed, the sexes are so unlike, that they would be taken for widely remote 
genera. The male is always inf erior in size, and also in organization, to the female. 
36. Whether certain individuals produce only male, and others only female young, or 
whether separate impregnations are required for the production of the separate sexes, I 
do not know; but from all my observations, I gather that the development of the one sex 
never takes place coetaneously with that of the other ; for male and female eggs are 
never seen attached to the same parent, and the immatm-e eggs in the ovary invariably 
develope themselves into the same sex as those which are akeady extruded. 
37. The duration of life in the male is always very brief. I have never been able to 
preserve one ahve for twenty-fom* hours. Their one business is to impregnate the 
females, which is the work of a few minutes, probably, in a state of freedom ; and for this 
momentary occupation no supply of loss by assimilation of food is wanted; and hence we 
can understand the lack of the nutritive organism. 
38. Some organs are found, with greater or less distinctness, in all. The (presumed) 
male of Hydatina senta received its names of Enteroplea and Organ-Jisch from Eheen- 
BEEG, on account of the copiousness of its internal organization. A muscular system is 
well-developed there, and in the males of Asplanchna and of BracJiionus Mulleri ; and, 
from the varied movements of all, its existence may be inferred where it is not detected. 
The frontal cilia are, in almost all cases, much more developed than in the females ; the 
result of which endowment is seen in the excessive rapidity with which the male shoots 
in all directions through the water. The great head-mass of granular substance is gene- 
rally distinct ; and in several cases (as in the Asplanchnce and in Br. Boreas and Mulleri) 
the great occipital ganglion is well-defined, with the red eye seated on it as in the other 
sex. Even where the ganglion is not apparent, the eye is conspicuous, with the excep- 
tion of Sacculus and Bolyarthra ; and m this last instance the small size of the animal 
must be borne in mind, and the density of the anterior parts. 
39. In the (presumed) male of Hydatina, in those of all the Asplanchnce, and of Brack. 
Boreas, there are organs answering to the lateral convoluted threads of the female ; and, 
in Aspl. Brightwellii, at least, these are accompanied by tremulous tags, and by a con- 
tractile bladder. 
40. A large mass of substance, which, being perfectly opake, appears black by trans- 
mitted light, but is white when the rays are reflected, is so generally found in male 
Eotifeea, as to be characteristic, though it is not universally present. I do not find it 
in the Asplanchnce, nor in Sacculus. On the other hand, I have observed it in the young 
of Stephanoceros, Floscidaria complanata, and F. cornuta\ and EheeI^beeg mentions it in 
F. ornata and Ladnularia. In Stephanoceros, it was certainly associated with well-deve- 
loped jaws ; and hence I presume it is not exclusively an indication of the male sex. 
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