Development of Rotifer vulgaris. 145 



accordance with this nothing was more natural than to regard 

 the motile filaments in the interior of the vacuole as sperma- 

 tozoids. 



There was yet another circumstance that strengthened me 

 in this conviction. Thus one day I observed that some of 

 my examples of Rotifer were endowed with remarkable sac- 

 like appendages, which were always situated exactly at the 

 spot where the micropyloid aperture of the " egg " passed 

 out through the cuticle. I observed these little sacs for 

 hours, but could not at first arrive at any conclusion as to 

 their nature. I only obtained an idea of how firmly they 

 must adhere to the Ilotifer, because they kept their position, 

 as if firmly rooted, in spite of the rapid movements of the 

 animals through whole masses of algal growth. After some 

 time I happened to make a few preparations (merely in order 

 to see whether the glass vessels still had living inhabitants), 

 and then I succeeded in observing the following process in 

 one of the saccules : — 



In the apparently homogeneous contents of this a vacuole 

 suddenly made its appearance (fig. 8, a), and moved downwards 

 (towards the micropylar structure) pretty rapidly. The passage 

 of the vacuole through the opening in the cuticle actually took 

 place, and then immediately there appeared within the u egg" 

 a small vesicle of the same kind, only rather smaller (fig. 8, b). 

 A portion of the original vacuole remained behind in the neck 

 of the micropylar orifice. Where the vacuole first appeared 

 in the saccule a sharply contoured fissure made its appear- 

 ance, which, however, soon showed dissolving margins, and 

 finally disappeared altogether. Two minutes afterwards a 

 new vacuole formed at the same spot as before ; but this imme- 

 diately broke up into two smaller ones (fig. 8, c), and both these 

 again took their course towards the micropyle. This time 

 both passed into the vesicle, so that now three such structures 

 were present in it. Two of these, however, soon fused toge- 

 ther, and then only two remained ; but in about fifteen 

 minutes these also united and caused the formation of a single 

 larger cavity in the interior of the ovate vesicle. 



All these remarkable processes I believed to be connected 

 with a hitherto overlooked sexual mode of reproduction in 

 Ilotifer vulgaris, and this the more because the saccules vividly 

 remind one of the spermatophores of many Crustacea (Cyclo- 

 pidse). 



Prof. Ehlers (of Gottingen), however, called my attention 

 to the fact, that years ago (1872) Prof. Friedrich von Stein 

 (of Prague) described, before the meeting of naturalists at 

 Leipzig, an Infusorial parasite belonging to the order Suctoria 



