ON THE REPRODUCTIVE SYSTEM IN THE HYDROIDA. 419 
A curious observation of importance in the present inquiry was made by 
Kolliker*, who found at Messina, in the stomach-cavity of a 10-tentacled 
medusa, evidently belonging to the family of the Mginide, and which he 
describes under the name of Zurystoma rubiginosum, Koll., a number of small 
organisms, resembling medusie in various stages of development, and which 
he believed he could follow from stage to stage until he found them assume 
the form of a 16-tentacled medusa. To this last, which, as is evident from 
his description, also belongs to the family of the diginide, he gives the name 
of Stenogasier complanatus, Koll. 
The great difference between these two meduse appears to Kolliker suffi- 
cient proof that the one could not have been produced by the other, and he 
regards the young Stenogasters as included accidentally in the stomach of the 
- Eurystoma. He views, however, the young brood of Stenogaster, exhibiting 
as it does various steps in a metamorphosis, as affording evidence of the 
direct development of Stenoyaster from the egg. It is, nevertheless, plain 
that there are no more valid grounds for such a conclusion in this instance 
than in Miiller’s case of Aginopsis. 
Some very valuable observations bearing upon this subject have been 
made by M‘Crady +t on another member of the diginide. He observed lying 
free in the umbrella-cavity of one of the Oceanide, to which he gives the 
name of Turritopsis nutricula, M°C., multitudes of little animals, presenting 
various forms, from that of a minute club-shaped hydroid to that of a well- 
developed medusa belonging to the type of the AZyinide, and all undoubtedly 
connected with one another as stages of a simple developmental process. 
Though he at first believed these to be the proper offspring of the Turri- 
topsis in which they occurred, he afterwards rejected this notion, and recog- 
nized in them the young of a species of Ounma (Cunina octonaria, M°C.), 
which had selected the umbrella-cavity of the Oceanidan in order to spend 
there as parasites the early stages of their existence. 
M°Crady views this case as presenting an instance of direct development 
from the ovum, believing that the Cunina originally gained access to the 
umbrella of the Turritopsis in the condition of a free-swimming planula. 
The untentaculated, club-shaped larva (the earliest stage observed) was fol- 
lowed by a bitentaculate hydroid form with long imperforate proboscis and 
distinct internal digestive cavity; and he noticed the interesting fact that 
this bitentacular stage freely repeats itself by budding. Next, two other 
tentacles make their appearance symmetrically between those first formed, 
_ while the extremity of the proboscis seems now to be perforated by a mouth. 
_ The umbrella next begins to make its appearance by an annular extension of 
the circumference of the body just below or at the oral side of the roots of 
the tentacles; and four new tentacles begin to sprout between those already 
formed, while lithocysts become developed on the margin of the incipient 
umbrella. After this the larva assumes the form of an adult Cunina in all 
essential points, except in the possession of a long proboscis, like that of a 
Geryonia, in which stage it leaves the umbrella-cavity of the Turritopsis to 
spend a free life in the surrounding water. It is only after it has quitted 
the medusa on which it had been hitherto living as a parasite that it loses 
‘its proboscis, and that the digestive cavity thereby assumes the form charac- 
teristic of the family of the Zginide. 
M°Crady’s observations are made with great care, and the various steps in 
the transformation have been fully and satisfactorily traced; but still there 
* Zeit. f wissen. Zool. 1843, p. 327. 
+ Proc. Elliott Soc. Nat. Hist. Charleston, 1856, p. 55. 
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