324 136 



elements of different kinds ; real blood cells have hitherto never been observed with 

 certainty. In the body cavity of the females Spermatozoa which are often observed 

 may be found swimming round in the fluid for a long time after pairing. In the 

 plancton Rotifers it seems as if the body cavity often contains large quantities of 

 oil globules; whether these are deposited in the hypodermic cells or are lying free 

 in the body cavity it is difficult to say, but as I have seen them move when the 

 animal is pressed, I have supposed that the last supposition in some cases may be 

 correct; in the same species thej' may be developed to very difl'erent degrees, upon 

 the greater or smaller quantities the hyalinity of the animal often depends. The 

 quantity of oil is greatest in the newly hatched animals and may almost disappear 

 when they have lived their longest time. It differs very much in the different families 

 and species; in some of them it is verj^ large, in others f. i. in most of the As- 

 planchnadœ it is almost entirely absent. 



In the male sex, especially in the plancton Rotifers, it may be shown that the 

 oil globules are mainly deposited on the dorsal side and that often a single, very 

 large one, may be found almost in the middle of the animal, above or just before 

 the testis. This f. i. is the case with the male of Conochilns volvox, Flosciilaria, Notops 

 brachionus, Gastropus sfglifer, Ploesoma Hudsoni. In others f. i. Polyartbra platyptera 

 and Pompholijx sulcata large oil globules in different numbers are deposited above 

 or before the testis. In others again especially the Triarthra males and those of Pe- 

 dalion the globules are deposited quite irregularly throughout the whole body. 



Where, in the plancton Rotifers, we have a single oil globule or a few dorsally 

 situated fixed oil globules, I suppose that these globules have some bearing upon 

 equilibration; it may be due to them that the males, during swimming, are always 

 forced to turn the dorsal side upwards, preventing the rotating motion so characte- 

 ristic of almost all females of Rotifers, but only rarely observed in the males which, 

 contrary to the females, when swimming slowly, very often move in straight lines. 

 A constant rotating motion of the males I have only observed in the males of As- 

 planchna that, as mentioned above, are also wholly destitute of oil globules. 



Especially Plate and Eckstein, but also Masius and with regard to Apsilus 

 also Gast have stated that the body cavity contains threads and cells of connective 

 tissue. It must however be pointed out, that with specific methods connective tissue 

 has not hitherto been observed (Hijdatina Martini 1912, p. 601). It may be possible 

 that we really have to do with extremely fine muscle threads; as such I have re- 

 garded those threads which in the male sex are especially mentioned with regard 

 to the Asplanclma species. 



Now and then in some species we find, lying free in the body cavity, greater 

 or smaller quantities of dark, often yellow coloured irregular masses; in the species 

 they may in some specimens be comparatively large, in others they are but small 

 or almost absent; their places differ from specimen to specimen, and it is most 

 probable that they diminish with age; they are very conspicuous e. g. in the As- 

 plandma species. They have often been observed, and have always been regarded 



