Natural History of the Vorticellge. 469 



with placental disks. This, however, is only a more or less 

 probable supposition, which, for the present, is destitute of that 

 support of actual observation which alone could prove it. 



Moreover, in one and the same species, namely Ejnstylis 

 jlavicanSj besides the gemmiform unions, I have made ex- 

 tremely remarkable observations of another kind, which also 

 indicate a mode of reproduction, but of a very different nature. 

 These may be briefly noticed here at the close of this com- 

 munication. Like most of the Vorticellse, Epistylis jlavicans 

 possesses a cord-like nucleus, bent more or less into a horse- 

 shoe shape. Frequently this nucleus, in all the individuals of 

 the stock, is filled only with a finely granular and otherwise 

 homogeneous parenchyma (PI. XV. fig. 10) ; but sometimes 

 the nuclei of Epistylis jlavicans exhibit very remarkable 

 alterations. In the first place we sometimes find individuals, 

 almost always several upon the same stock, the nucleus of 

 which is considerably thickened, but at the same time shortened, 

 so as to acquire the form of a somewhat crooked sausage, 

 which, by its dark contents, shows sharply from the interior, 

 and therefore catches the eye even under a low power and in 

 the living and moving animals (PI. XV. fig. 9). If the 

 nucleus of this form be examined more closely, and with a 

 higher power, we see that it acquires its dark appearance 

 from a mass of capillary structures with an undulating 

 course, which give the whole organ the appearance of being 

 filled with a ringlet-like mass of filaments resembling sperma- 

 tozoids (PI. XV. fig. 5, n). No movement can be detected 

 in them. If this substance be isolated by tearing or bm-sting 

 the nucleus, we find that it consists of nothing but capillary 

 bacilli, slightly curved in a sickle-like form, which appear to 

 be a little dilated at one end and pointed at the other. All 

 are rigid, dimly shining, and sharply defined (PI. XV. fig. 6). 

 These, no doubt, are similar structures to those first found by 

 Johannes Miiller and his pupils Clapar^de, Lachrhann, and 

 Lieberkuhn, and afterwards by Stein, Balbiani, and others, in 

 the nucleus and nucleolus of many other Infusoria, and which 

 have subsequently been regarded as the spermatozoids of the 

 Infusoria. One is very much inclined, in the present case, to 

 regard the structm-es in question in E. Jlavicans ^ from their 

 whole mode of occurrence and appearance, as spermatozoids. 

 However, especially taking into consideration the " gemmi- 

 form conjugation " which occurs in this species also, I do not 

 venture at present for my own part to treat these as the 

 spermatozoids of the Voi'ticella3, as has already been done by 

 others, perhaps too definitely, although, of course, I am no 

 more inclined to accept the second supposition, that they are 

 parasitic structures. 



