416 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Splanchnic Musculature in Oligochseta and Hirudinea.* — N. 

 Livanow notes that the general statement in regard to the musculature 

 of the intestine is, that the internal layer consists of circular fibres and 

 the outer of longitudinal fibres. In Branchiobdella varians and Haplo- 

 taxis gordioides (syn. Phreorgctes menlceanus) the arrangement is the 

 reverse. The same is true of Acanthobdella, but in Lumbriculidse, 

 Enchytrreidas, and terricolous Oligochseta, the circular muscles are in- 

 ternal and the longitudinal external. Livanow comments on the possible 

 theoretical import of the two types of muscle-arrangement. 



Nematohelminthes. 



Cerebral Ganglion and Body-Cavity of GordiidaB.f — Max Runther 

 finds that in architectural plan and in the minute structure of the 

 various systems, the genus Gordius betrays remarkable affinities with the 

 Archiannelida, especially as regards cuticular structure, nervous system, 

 musculature, parenchyma, and gonads. He deals especially with the 

 cerebral ganglion and the body-cavity, and the general result is that 

 Gordius is nearer to Polggordius than to typical Nematodes. 



Radially Striated Ganglion Cells in Ascaris.J — R- Goldschmidt 

 describes these remarkable and characteristic cells, which occur through- 

 out the nervous system of Ascaris. The ganglion cell is surrounded by 

 a glia-capsule, externally bounded by a firm lamella, and consisting of 

 numerous extremely fine concentrically-disposed membranes traversed by 

 equally fine radial lamella;, like an intricate spider's-web. From the 

 capsular wall numerous radial processes penetrate into the cytoplasm in 

 the direction of the nucleus, and end in the internal finely vacuolar 

 plasma. In the cytoplasm the processes run in fine tubes. 



As to the physiological meaning of this intricate structure, Gold- 

 schmidt thinks that a trophic function is improbable, and inclines to 

 attribute to it a mechanical role. It makes the cell more sensitive to the 

 vibrations and oscillations which affect the body generally. 



Platyhelminth.es. 



Development of Turbellarians.§ — E. Bresslau gives a large number 

 of facts regarding the development of the Winter and Summer eggs of 

 Mesostomum ehrenbergi, M. lingua, etc. The Winter eggs of all the forms 

 are very numerous : they have abundant yolk-cells, and are enclosed in a 

 thick brown-coloured shell. The yolk-cells blend into a thick yolk-mass, 

 in the midst of which the germinal material lies. The epiderm has a 

 paired origin ; the gut and schizoccele arise by indifferent cells of the 

 embryo laying themselves around cavities which have previously appeared 

 in the yolk-mass. The Summer eggs of 31. ehrenbergi have a very small 

 number of yolk-cells, which contain only minimal yolk-masses. The 

 egg-membrane is thin, transparent and colourless. The yolk-cells dif- 

 ferentiate into enveloping and vacuole cells, while the germinal substance 



* Zool Anzeig., xxvii. (1904) pp. 585-9. 



t Tom. cit., pp. 606-14 (4 figs.). 



% Iliol. Centralbl., xxiv. (1904) p 173-82. 



§ Zeitschr. wiss. Zool., lxxvi. (1904) pp. 213-332 (7 pis.). 



