6 Dr. A. Krohn on the Structure and 
maturity approaches, the more strongly does the dorsal surface 
of the parent become inflated, the ectoderm being continually 
removed further from the endoderm. When the embryos are so 
far developed that the period of their escape approaches, the 
dorsal surface appears elevated into a corresponding number of 
roundish humps. At last these humps of the ectoderm burst 
one by one, and thus the young are set free in a corresponding 
order*, 
The male of Eleutheria appears to be very rare. I only had 
the opportunity of observing it once. Like the eggs in the 
female, the semen in the male is produced in the back, between 
the ectoderm and endoderm. In the male alluded to, the 
back appeared to be much distended by a considerable quantity 
of the semen, which shone through the ectoderm as a chalky 
white mass. Minute floccules of this perfectly mature semen, 
artificially set free by tearing the ectoderm, proved to be com- 
posed of thousands of remarkably active spermatozoa, charac- 
terized by a bacilliform head, and a long tail running out into a 
fine point at the extremity. 
I now come to speak of the second mode of reproduction, 
namely that by gemmez. This occurs not only in the asexual in- 
dividuals, but also—which is worthy of notice—in those which 
are sexually perfectly developed. Thus most of the females which 
came under my observation, small as their number might be in 
comparison with the great quantity of asexual individuals, bore 
more or less developed buds; and this was the case also with the 
male above mentioned +. 
The bud appears at first in the form of a small, rounded ex- 
crescence upon the back of the parent animal, close to the peri- 
phery of the body, in one of the interbrachial or interradial 
spaces. At its earliest origin it is nothing but a diverticulum 
of the annular vessel, which during its increase has pushed the 
ectoderm before it, and raised it into a mound. It consequently 
consists of two superposed layers (the ectoderm and endoderm) 
and of a cavity communicating with the gastro-vascular system. 
* From this there seems to be no doubt that the creature met with by 
Hincks in the somatic cavity of one individual, and regarded by him as a 
free embryo, which, after repeated endeavours to get out, always returned 
again into the cavity, is to be considered only as an animal (probably a 
Copepod) which had either got accidentally into the stomach or had been 
swallowed. 
+ My investigations, as already stated, were made in the first half of 
May. It appears from the observations of Quatrefages that at other seasons 
the formation of buds entirely gives place to sexual reproduction. “This 
naturalist says expressly that he did not detect the slightest indication of 
buds on specimens of H. dichotoma observed during the summer months; 
so that their increase during this period is probably effected exclusively by 
eggs. 
