286 98 



see any eyespot, but oTcr the forepart of the brain two bright double, contoured 

 light refracting spots, which are most probably openings from a retrocerebral organ 

 ■which has not been observed. Neither dorsal nor lateral antenna? observed; nor ex- 

 cretory organs: alimentary canal seems to be wholly wanting. A large piriform 

 testis, containing two sorts of spermatozoa, ending in a ductus seminalis coated 

 with cilia and with a tuft of small cilia at the opening, this situated somewhat 

 ventrally; large prostata glands. When swimming the animal shows no peculiar 

 structural features behind, but when it is pressed below the cover a little tap appears, 

 provided at its tip with a styliform body, perhaps a seta. In this tap lies a rather 

 large gland-like body, immediately over which the prostata gland lies. I regard this 

 tap as the rudiment of a foot, and the gland as the foot gland. Above the testis lies 

 a very large light refracting oil globule and between it and the brain a large glob- 

 ular opaque bod)-, containing numerous sharply edged small bodies. Only a few longi- 

 tudinal muscles have been seen. At a first glance and, when the animal is swim- 

 ming, the whole body is almost quite opaque, filled as it is by a greyish mass 

 with many small oil globules. It is only by means of pressure that the internal 

 structure has been somewhat elucidated. Size of male 80 //, of female 170 — 200 /(. 

 Time 1 Mil 21. In a plancton sample which only contained this species, Polyarthra 

 and Synchœta. 10 specimens of the above described peculiar male appeared. 



Ascomorphidae. 



This little family comprising the two genera Ascomorpha and Anapus may best 

 be connected with the fam. Gastropodidce ; de Beauchamp refers the genus Ascomorpha 

 to this family. It differs from it in very essential points; its systematic position and 

 restriction has always been difficult; owing to want of foot it was formerly referred 

 to the fam. Asplanchnadœ, with which it has no affinities at all. It comprises such 

 different forms as Ascomorpha (= Sacculus) viridis Gosse; Ascomorpha saltans Bartsch 

 (= A. agilis Zach). Also the genus Anapus is referred to this group. 



In my opinion the whole group is very unnatural. The Ascomorpha (= Saccu- 

 lus) viridis Gosse has only slight affinities to the other Ascomorpha-S'pecies. A. saltans 

 Bartsch, which is perhaps identic with A. agilis Zacharias is well known to many 

 planctologists, but almost unknown in the literature relating to Rotifera; the genus 

 Anapus differs in all essential points from Ascomorpha. 



Sacculus viridis is common in the vegetation zone of smaller ponds; it carries 

 its eggs, female as well as male eggs. 



Ascomorpha saltans and the genus Anapus with the two species A. tesfudo 

 Lauterb. and A. oucdis Bergend, are all typical plancton organisms in the pelagic 

 region of smaller lakes, but especially in the central free parts of ponds. The spe- 

 cies prey upon the Dinoflagellata (Ceraiium hirundinella, Peridinium), which they 

 suck out. whereupon the empty hyaline carapaces fall to the bottom. Their maxima 

 coincide with those of the Dinoflagellata. The eggs are laid upon other plancton 

 organisms, especially Uroglena volvox. In my opinion the genus Anapus may be 



