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48 SUMMARY OF CURRENT RESEARCHES RELATING TO 



capturing and paralysing Copepods. Starving brings about reduction 

 of size. The creatures showed great indifference to high temperatures 

 (30° C.) and scarcity of oxygen. The number of arms varies from five 

 to twelve, and a temporary absence of oxygen causes a developing bud 

 to become an arm attached to the parent medusoid. Wounds are 

 quickly healed, two portions can be united readily ; there is great 

 regenerative capacity ; in short, there is extraordinary plasticity. 



Germ-cells of Leptomedusaj.* — I. Apstein has studied the history 

 of the germ-cells and the development of the gonads in Octorchis gegen- 

 lauri and other Leptoniedusse. In Octorchis the ova always differentiate 

 in the ectoderm. The oocytes of the first order appear in association 

 with the endoderm. The ova dispose themselves with their maximum 

 surface on the supporting lamella, become attached to it, and are 

 surrounded by it. The older ova lie topographically in the endoderm, 

 but they are really in the supporting lamella. Those that get free 

 from this come to nothing. The ova have always a membrane. Their 

 food is fluid. They show no amoeboid movement, nor any formation of 

 a syncytium. Environmental influences have a demonstrable effect on 

 the history of the ova. There is no true migration. The germ-cells 

 are moved by an extension of the germinal zone, not by their own 

 movement. In some other cases, such as Euchilota maculata, Obelia, 

 Phialidium, the ova differentiate in the endoderm. Whether the germ- 

 cells differentiate in the ectoderm or the endoderm, their definitive 

 position is in the supporting lamella. The male germ-cells always 

 appear in the ectoderm, but become embedded in the supporting lamella. 



Nematocysts of Polykrikos and Campanella.f — E. Faure-Fremiet 

 describes in the Dinoflagellate Polykrikos nematocyst-like structures, 

 to which Biitschli has previously called attention. Besides trichocysts 

 there are explosive nematocysts (ten to fifteen in number hi all indi- 

 viduals) which pass through a trichocyst-like stage. In some specimens 

 of the large Vorticellid Gampanella umbellaria there are somewhat 

 similar structures which require further study. The author found 

 only one instance. They differ from the nematocysts of Polykrikos 

 not only in being inconstant, but in their minute structure. 



Porifera. 



Hexactinellid and Radiolarian Spicules.^ — A Schwan makes an 

 interesting comparison between these, showing how much they have in 

 common in architecture and disposition. They serve similar functions, 

 giving the living substance support, cohesion, and elasticity. 



Protozoa. 



Inheritance of Size in ParamoBcium.§ — H. S. Jennings and K. S. 

 Lashley find that, as a result of conjugation, the progeny of the two in- 



* Zool. Jahrb., xxxvi. (1913) pp. 579-616 (2 pis.). 



t G.R. Soc. Biol. Paris, lxxv. (1913) pp. 366-8. 



t Zool. Jahrb., xxxiii. (1913) pp. 603-16 (11 figs.). 



§ Journ. Exper. Zool., xv. (1913) pp. 193-9. 



