420 SUMMARY OF CURRENT RESEARCHES RELATING TO 



lungs of frogs, and finds that the nuclei of the blastomeres show a re- 

 markable periodic movement, at times rising to the periphery of the 

 cell, and then sinking again within the cytoplasm. A series of time 

 observations on segmenting eggs showed that the movements are not a 

 mutter of chance, but take place accordiug to definite rules, formulated 

 by the author as follows : — The nucleus begins to approach the cell- 

 periphery as a division is finishing, it remains at the point of contact 

 for several minutes, then begins to travel inwards to begin the new 

 division ; the place of contact always lies in the plane which forms the 

 next division-plane, and the segmentation furrow appears at the point 

 of contact. Similar conditions were found by the author to obtain in 

 several other Nematodes (species of Strong ylus, Sclerostomum, &c), but 

 the phenomenon apparently does not occur in all. As to the significance 

 of the movement, the author associates it with the accelerated growth of 

 the cell-periphery, which makes segmentation possible, and finds in it 

 a confirmation of his view that the nucleus is a store of food -material 

 (Stoffmagazin), not a centre of force. 



Germinal Layers in Nematodes.* — A. Conte has studied these in 

 Cucullanus elegans Zed. and in the Filaria of the green frog. As 

 previously, for Sclerostomum equinum, he finds a more or less considerable 

 disappearance of the ectoderm and a total disappearance of the endoderm. 

 The alimentary canal of the adult is formed in part by ectodermic ele- 

 ments constituting the oesophagus, and in part by mesodermic elements 

 constituting the intestine. In all these three viviparous forms the 

 general cavity is lined by two layers of mesodermic origin. 



Oxyuris curvula and 0. mastigodes.f — Max Jerke has investigated 

 the characters of these two nematodes from the horse, together with 

 their life-history, effect on the host, and so on. He finds the two to be 

 good species, though they are very nearly related ; the differences between 

 the males exclude the possibility of there being only one dimorphic 

 species. As regards the life-history, the ripe females lay their eggs in 

 the vicinity of the anus, and then die. The eggs remain here within a 

 sticky mass for a few days, then fall to the ground, to be again ingested 

 with food. Within the stomach of the host the investment dissolves, 

 and the young worms find their way usually to the crecuni, where they 

 live upon the ingested food. They are not parasites in the strict sense, 

 and cause only symptoms of local irritation about the anus. The eggs 

 will not develop without access of oxygen, wherefore development does 

 not occur within the gut of the host. 



Platyhelminthes. 



Poison of Parasites.! — Dr. P. Mingazzini prepared with careful 

 j>recautions extracts of Taenia cucumerina (Dipylidium caninum), Moniezia, 

 Ascaris lumbricoides (from the pig), and Echinorhynchus gigas, and tried 

 the effect of the fluids on Protozoa and as injections into rabbit, cat, 

 dog, guinea-pig, and pigeon. It always had a poisonous effect. The 



* Comptes Rendus, cxxxii. (1901) pp. 1064-6. 



t Jenaische Zeitschr. Natunviss., xxxv. (1901) pp. 347-408 (1 pi. and 4 figs.). 

 % Rass. Medicina Moderna, Ann. ii. No. 8 (1901) 20 pp. See Zool. Centralbl., 

 viii. (1901) p. 226. 



