292 Dr. F. Leydig on Hydatina senta. 



what he regards as cylindrical tremulous organs are trumpet- 

 shaped ones seen in longitudinal section ; from their flat nature, 

 they then appear cylindrical. When Cohn becomes acquainted 

 with true cylindrical, uniform tubes, such as occur, for example, 

 in Notommata Sieboldii, he will perceive the difference of form 

 between the two. 



The fluid which fills the abdominal cavity, washes the viscera, 

 and forms the analogue of the blood, in individuals which had 

 been plentifully fed with Euglena viridis, contained numerous 

 clear globules, or blood-corpuscles, of a roundish form and un- 

 equal size. It was remarkable to meet again in Hydatina senta 

 with the same structures which I had formerly, as a matter of 

 supposition, attempted to indicate in Lacinularia as spermatozoa*, 

 and afterwards arranged in the series of parasitic formations. 

 They are globular bodies with sharp outlines j their margin is 

 furry, as if with a fine coat of hair. Towards the end of March 

 the entire abdominal cavity of many individuals was so filled 

 with these globules, that the animal appeared strongly white by 

 reflected light. However, the individuals thus affected swam 

 about just as briskly as those which exhibited nothing of the sort. 



The clavate bodies in the tail consist of a delicate envelope and 

 pale molecular contents, in which beautiful nuclei, each with a 

 nucleolus, may be distinguished; in many individuals, small 

 fatty points are also present in variable amount. I regard the 

 organs in question as glands, which in their position and func- 

 tion correspond with the caudal glands of Enoplusiov example f ; 

 they open at the apex of the caudal appendages [Fusszangen) ; 

 and as the worm just mentioned "can attach itself firmly to the 

 object-bearer by the posterior extremity of the body, in order to 

 carry the body round this point with a waving motion," so also 

 can the Hydatina fix itself by the tips of the caudal appendages, 

 probably by means of the sticky substance excreted here. It 

 seems to me also that in a certain upright position of the caudal 

 appendages, I have detected the opening at their tip. 



The hairy coat of the " winter eggs," which Ehrenberg, in 

 opposition to R. Wagner, declared to be an Alga, Hygrocrocis 

 vestiens, is distinctly perceptible even on the eggs in the ovary. 



The male Hydatina, or the Enteroplea Hydatina of Ehrenberg 

 (PI. VIII. fig. 3), is certainly considerably smaller than the female, 

 but has the same outline of body, and even the rotatory organ 

 is notched on the ventral side, as in Hydatina senta. This struc- 

 ture is seen with certainty in animals which tumble about freely 

 without being annoyed by a glass cover, and thus turn their 

 rotatory organs to the beholder from all sides. Cohn erroneously 



* Zeitschr. fiir wiss. Zool. 1851. 



t MuUer's Arcliiv, 1854, tab. 11. fig. 12. 



