270 82 



They belong to the largest known Rotifer males, reaching about 500 n; as far as 

 we know, they never present variation in outer form; thej' are not polj'morphic, and 

 if they belong to species where females in one of their forms are humped, they are 

 always humped. 



The wheel-organ and disc differ but little from those of the female; the ali- 

 mentär}' canal is always rudimentarj-, best developed as suspensor testis with a rudi- 

 ment of a mastax in A. priodonta; very short in A. amphora and totally absent in 

 A. Brightwelli and A. Sieboldi; in these species the testis is only supported by strong 

 muscles. The nerve sj'stem is constructed in accordance with that of the female, and 

 so are the different sensitive organs. This is also the case with the excretory organ; 

 the number of vibratile tags correspond with those of the female, and a large con- 

 tractile vesicle is always present. There is great coincidence with regard to the muscle 

 system, peculiar is the great development of fine muscle threads below the cuticula. 

 Whether the ovary is horseshoe-shaped or globular in the female, the testis is always 

 globular; there is no real penis, the ductus seminalis opens into a canal in which also 

 the canal for the contractile vesicle opens; during the copulatorj' act the ductus semi- 

 nalis is pushed forwards, turned inside out and used as penis ; it has a wreath of cilia. 



Almost all observers have seen some globular bodies different in size and num- 

 ber, lying in different parts of the body. They are commonly (Levdig, Hudson) re- 

 garded as stored nutriment for the males, which have no possibility of getting food; 

 they derive from yolk masses, which the embryo has not used. Lange (1911, p. 439) 

 has shown that this supposition is correct. He saj's as follows: "1910 züchtete ich 

 A. Biigthwelli und habe dabei ein c/ 7 Tage lang lebendig erhalten. Die darauffol- 

 gende Untersuchung des Zellhaufens ergäbe, dass er sich während dieser Zeit fast 

 völlig aufgezehrt hatte. Auch für A. Sieboldii habe ich in allen Fällen nach 1 — 2 Tagen 

 eine starke Abnahne in den Flächenausdehnung und Dicke des dorsalen Zellen- 

 komplexes konstatiert." I can further remark as follows. The Asplanchna males most 

 probably belong to those with the greatest longevity. Powers has kept them alive 

 for 2—4 days (1912, p. 534). Lange for 7. I myself for 4. I have isolated males, 

 whose birth I have observed; they had, at birth, a size of about 300;«, when they 

 died four days later, the size was about 400 /(. At birth there was a great deal of 

 store nutriment, at death it had disappeared; growth after birth has hitherto not 

 been observed in Rotifer males. 



Rattulidæ. 



The family comprises the two genera Diurella and Rattuhis. The males in this 

 family have hitherto been quite unknown. Characteristically enough, Jennings, in 

 his excellent monograph of the familj' (1903 a, p. 273), does not mention the males 

 with a single word. 



The males of the genus Diurella are still unknown; of the genus Rattulus I 

 have found the males of three species. 



