188 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Nervous System of Tricladidae from Baikal.* — H. Sabussow has 

 studied species of Sorocelis Grube, Rimacephcdus Korotneflf, and Planaria 

 Miiller, from Lake Baikal, with especial reference bo the nervous system. 

 As in other triclads, it consists of a brain, two ventral longitudinal 

 strands, and a nerve plexus in close relation to the integumentary mus- 

 cular layer, and especially developed on the ventral surface. 



The main mass of the longitudinal strands consists of a glia frame- 

 work, formed from the fibres or lamellae, secreted from the numerous 

 glia cells. The nerve cells are relatively few, and occur in the spaces 

 bounded by glia cells. A characteristic peculiarity of the nerve cells is 

 the differentiation of fibrillar structures in the protoplasm. The nerve 

 cells seem to be inter-connected by fibrils, passing from one element to 

 another, so that a sort of network is formed. 



Excretory System of Fresh-water Triclads.f — J. Wilhelmi supplies 

 some notes on the structure and course of the excretory canals, based 

 on observations on Dendrocoelum lacteum, Plan or in ///pin a, P. torva, P. 

 gonocephala, and Polyceli* nigra. The main and side branches are lined 

 internally by a membrane. The wall consists of a highly granulated, 

 almost homogeneous mass, which passes over without limiting border 

 into the mesenchyme. Flame cells are not present in the main stems of 

 Dendrocoelum or Planaria alpina. P. alpina appears to have a large 

 number of external openings, but the question is difficult to elucidate. 

 The author failed to find the network of vessels described by Chichkoff. 

 Flame cells occur only in the mesenchyme, and not in the gut epithelium. 

 The system in fresh-water triclads resembles in essentials that of Cestodes 

 and Trematodes, but is distinguished from that of both by the mode of 

 opening and the absence of transverse anastomoses. In the course of 

 the main stems, the segmental arrangement of the clump formations, 

 and dorsal openings, the fresh-water triclads resemble the marine Gunda 

 segmentata. 



Viviparity in the Eumesostominae.J — E. Sekera describes and dis- 

 cusses the significance of viviparity exhibited by 3fesostoma ekrenoergi, 

 M. lingua, etc. The young, arising from summer eggs, break through 

 the mother's body at some point which can heal readily. The parent's 

 vitality is unimpaired, and she produces resting eggs later. These 

 summer animals do not usually produce summer eggs. The author 

 considers the formation of the summer eggs, and the accompanying 

 viviparity as a parallel phenomenon with asexual reproduction by 

 division, as seen in the Stenostomida? and Microstomida3, whereby a very 

 rapid and abundant multiplication of individuals is effected. 



Rotifera. 



Three New Parasitic Rotifers. — Sebastiano Piovanelli § describes 

 Distyla branchicola, a new parasitic species, living, in company with the 

 two Bdelloids previously described, in the branchial cavity of the 



* Zool. Anzeig., xxviii. (11)04) pp. 20-32 (4 figs.). 

 t Tom. cit., No. 7 (1904) pp. 268-72. 

 J Zool. Anzeig., xxviii. (1904) No. 7. pp. 232-43. 

 § Monitore Zool. Italiano, xiv. (1903) pp. 345-9. 



