322 134 



not only to drive noxious material, dermng from the metabolism, out of the body, 

 l)ut also and mainly the volumina of water which by purely physical causes are 

 forced into the body cavity. This supposition is by no means new; it has already 

 been set forth by Leydig (1855, p. 82). 



Remembering that in .4. priodnnta we only find about from 4 to 5 vibratile 

 tags and in A. Sieboldi from 40 to 50 it is possible that a more thorough observation 

 relating to the process of the filling of the bladder in these two species might per- 

 haps elucidate something with regard to the function of the organ; lack of material 

 has hindered me from making these investigations. 



I cannot see better than, that there is still, in the anatomy of the Rotifera, 

 an essential point relating to the excretory organ about which we lack almost all 

 knowledge. 



As we know that the Asplanchna males are most probably the males with the 

 greatest longevity (about 4 — 7 days) whereas the strongly reduced males most pro- 

 bably only live for some hours and never 24 hours, it seems to me that the pre- 

 sence of the contractile vesicle is more dependent upon the longevity of the animal 

 than upon the presence of a functioning alimentary canal. 



Different authors have supposed that we should find special pores in the cu- 

 ticula through which the water poured into the body cavity. Leydig (1855, p. 82) 

 has supposed something in this direction, and Ehrenberg regarded the dorsal organ 

 as a sipho. 



In this connection we may call attention to the fact, set forth by Krätschmar 

 (1908) but hitherto never corroborated, that the peculiar sac which contains the great 

 oil globule which is lying over the testis and which in some way "in enger Be- 

 ziehung zu dem sehr schwierig zu beobachtenden Excretionsorgans steht", by means 

 of a canal, ending in an always open porus, is in connection with the outer medium. 

 "Es ist unschwer einzusehen, dass diese Einrichtungen darauf abzielen ständig das 

 Excretionsorgan offen zu halten (1908, p. 9)." How great is the bearing of this ob- 

 servation, we do not really know. In this connection 1 take the liberty to call at- 

 tention to the fact, that 1 have with absolute certainty seen in Euchlanis that the 

 two lateral canals debouch in the sac above the testis and that 1 was unable to see 

 the canals follow the ductus seminalis to the opening of the penis. 



Muscles. Females. It is quite impossible in our present stage of know- 

 ledge to give a correct picture of the muscle system of the Rotifera. The muscles 

 may be divided into transversal muscles, longitudinal muscles and muscles belonging 

 to special organs, especially those of the mastax, the contractile vesicle and the 

 stomach. The transversal muscles are particularly well-developed in the Bdelloida, 

 where they often encircle the body at regular intervals to a number of twelve; they are 

 here commonly interrupted ventrally. In the other orders and families their number 

 is much smaller, commonly six or seven; extremely large only in Atrochus. In the 

 loricate Rotifers they are not so well-developed; in most of the figures and descrip- 

 tions they are wanting. The main task of the transversal muscle system is most 



