258 70 



dorsally to the hypodermal cells, further two parallel muscles which run ven- 

 trally aslope and are fastened with the other end near the globular body, the 

 presimied rudimentan,- mastax; these muscles bend the forepart of the body and 

 are able to give the corona a slanting position in relation to the axis of the 

 body; further the muscles which run downward, one more dorsally and two more 

 Tentrally. Finally we find on the ventral side two pairs of rather narrow very 

 long muscles, the one pair fastened with one end below the corona, with the other 

 to the outer end of the ductus seminalis, the other pair with the cleft to the glo- 

 bular body, with the other to the opening for the urogenital canal. ^\Tien this 

 muscle is contracted, the whole posterior part of the body is bent downwards and 

 forwards. Simultaneously with this, the muscles which are fastened to the opening 

 of the penis, are loosened and, partly by means of augmented pressure in the body 

 cavity and the numerous muscle threads in the cuticula, the testis is pressed down- 

 wards out into the urogenital canal. Transversally over the body are stretched some 

 transversal muscle bands, running between the dorsal and ventral muscle system. 

 A closer examination will further show a system of extremely fine muscle threads 

 which mainly form a very wide-meshed net-work, directly under the cuticula; where 

 these threads meet each other, we find a granular protoplasmatic structure, in which 

 often a nucleus is seen: this net-work is most developed in the hind part of the 

 body; where the threads meet each other, long, extremely fine, threads run down- 

 wards, mainly from the wheel-organ; if we observe a living Asplanchna, we shall 

 see that it very often alters its form; now this now that part of the cuticula is 

 drawn in and on the smooth surface of the body a larger or smaller hollow 

 may be shown; this power of altering its form comes from the muscle network; 

 if two specimens are compared, it will be seen, that it is never developed in quite 

 the same manner. 



As far as I have been able to see, in A. priodonta just as in the other specimens 

 here mentioned, we find two sorts of lateral canals in the excretory organ on 

 both sides of the body. The one may be described as a curved ribbon with strong 

 curves and knots; they are tubes of a loose granular substance, with clear nuclei 

 imbedded in their walls; at the sides of these tubes are the other sort; these canals 

 are straighter, narrower and their lumen is more hyaline; they carry four vibratile 

 tags; as far as I have seen, neither more nor less. 



The real connection between the two canals I have not been able to see. With 

 regard to the finer structure of the organ in the female I refer the reader to the 

 excellent paper of Willem (1910, p. 21). The canals debouch into the contractile 

 vesicle, which is very large; over its surface run a number of very fine muscle 

 threads meeting each other almost in the centre of the bladder; it opens in the 

 urogenital canal, very near the opening of the penis. To this point are further at- 

 tached two small, short muscles, fastened with the other end to the bladder. The 

 testis is rather small, pyriform, containing the two sorts of spermatozoa and opening 

 in a urogenital canal. When used under the mating process, the urogenital canal 



I 



