308 120 



high degree of perfection. This f. i. is thé case with the Raitiilidæ. With regard to 

 the significance of the asymmetry in the foot forms in this family I especially refer 

 the reader to Jenning's admirable paper. 



The foot of the Bdelloidœ which is used telescopically in creeping, and with- 

 drawn in swimming, is in manj^ species mainlj' an organ of attachment and the 

 foot provided with a series of until five pairs of foot glands, the glands lying above 

 each other. In the moss living Callidina species and Discopus it is only used as an 

 Organ of attachment, and here provided with a sucker. Also in the Flosculariidce and 

 Meliceriidce the foot is only an organ of attachment, but simultaneously, it has here 

 the rôle of carrying the fully distended animal back into the bottom of the tube 

 again when contracted. In accordance herewith it is provided with long powerful 

 muscles in fixed numbers. In the young freeswimming animals the greater part of the 

 foot is occupied bj' large foot glands; later on, when the animals have fastened 

 themselves, they atrophiate. Whether the peculiar stick-like appendages of Pedalion 

 may morphologically be regarded as parts of the foot is doubtful. 



Foot, male sex. If we will now try to take a survey of the different foot 

 forms in the male sex, it will soon be obvious that the differences here are by no 

 means so great as in the female sex. In the most primitive family, the Nofommatidæ, 

 the foot in the two sexes is almost of quite the same structure. It is also used quite 

 as in the female as a creeping organ and because the foot glands are alwaj's well 

 developed, also as an organ of fixation. In the males of the Synchceta the foot and 

 foot glands are much more reduced than in the female sex, the organ being here a 

 true appendix to the penis. In Hydatina and Rhirwps it is well developed, reduced 

 in Notops brachionus, and still more in Brachionus ; the foot is here not retractile as 

 in the female sex; it is short and thick, is never used as a steering organ and only 

 for attachment. Very often the Brachionus males swim with the enormous penis 

 fully evaginated and with the foot then hanging downwards as a small venti-al 

 appendage. In the Anurœa there is no foot at all either in the male or the female 

 sex; at a first glance it looks as if the males are provided with a long fleshj' appen- 

 dix that looks like a foot; this is however only the long penis which, especially in 

 A. hgpelasma, is flexible and is used in some way as a steering organ during the 

 swimming motion. It is always protruded. In G. hyptopus the foot in the male sex 

 is very inconspicuous and always carried retracted; only during the copulatory act 

 it is protruded together with the penis, then hanging downwards as a small incon- 

 spicuous appendage. In Gastropus stylifer the female sex has a remarkable narrow 

 foot without toes while in the male sex it is reduced to a verj' inconspicuous st^'liform 

 process, but provided with a comparatively large foot gland. In some genera in which 

 the female has a foot (Ploesoma, Rcdtulus) the foot in the male sex is wholly wanting, 

 and in all those genera where the female sex has no foot at all, it is also absent 

 in the male sex. As regards the freeswimming Rotifers, where the foot is used as 

 a steering organ, it is only among the Eiichlanidcc and Scdpinadcc that it is used in 

 that way also in the male sex where it is used as a leaping organ in the female 



