306 118 



born females which only attain hyalinity during growth. In the few cases where I 

 have been able to observe the longevity of the males (Asplanchna, Hydatina) I have 

 seen that the males, too, are more transparent in the last part of their life and that 

 just these males grow larger during the few days they live. The greater hyalinity is 

 most probably due to the spreading out and flattening of the hypodermic layer 

 behind an always increasing surface; this will especially be understood when we 

 remember that the males get no food during life. 



If the body of the female is covered with a lorica, the lorica of the male may 

 in some and relatively few cases be a true picture of that of the female; this is 

 the case with the lorica in the hitherto known specimens of Salpina and Euchlanis 

 perhaps also in Metopidia. In those species in which we commonly do not speak of 

 a real lorica but in the cuticula of which we find characteristic keels and furrows 

 f. i. A'^. hyptopus, we find this sj'stem again in the male. 



In the great families of loricate Rotifers : Brachionidœ and Anurœadœ in which 

 the lorica in the female reaches almost its highest development, we can hardlj' speak 

 of a true lorica in the males ; there exists a rather thick cuticula, provided with some 

 conspicuous and constant keels and furrows which are not as a rule in accordance 

 with anything in the structure of the lorica of the female; the facettation of the 

 lorica which is so highly characteristic of that of many of the females, is here 

 wholly wanting. 



This lorica is further characterised by the peculiar, commonly strongly developed 

 spines at the anterior and posterior ends; we do not know any equivalents to these 

 spines in the males. It is a peculiar fact, that the males of the Rotifers even if the 

 females have highly developed spines, hardly ever possess spines of any kind. Apart 

 from the Brachionidœ and Anurœadœ, this also holds good for the Triarthra and 

 Polyarthra, further for all the hitherto known males of Rattulidœ and Dinocharidœ. We 

 only meet with spines similar to those which we find in the lorica of the females, in 

 the Salpinadœ and in the peculiar spiny process on the head of Colurellidœ. Where 

 the lorica presents peculiar structures in the female sex, these peculiarities are ab- 

 sent in that of the males; we have in the males no facettation of the lorica and no 

 anterior ring of plates in the faintly developed lorica of Dinocharis (Weber) and no 

 hint of the peculiar foam-like structure of the lorica of Ploesoma hudsoni 9 . Further 

 we never find any trace in the males of that peculiar yelly envelopment so char- 

 acteristic of the female of Copeus labiatus. 



Foot. Female sex. Especially among the creeping Rotifers with ventrally 

 situated disc the foot is not sharply separated as a special organ from the other 

 part of the body. It consists of from two to four "segments" w'hich are feebly tele- 

 scopic; on the last "segment" it carries two toes which are provided each with a 

 foot gland. By means of sticking material from these glands the animals are able to 

 fasten themselves to a substratum. A foot of this structure is designated as a creeping 

 or crawling foot and is mainly found in the Notommatidœ: bj' means of the sticking 

 material from the foot glands the animals now and then fasten themselves to the 



