68 SU.MMARY OF CURHENT RESEARCHES RELATING TO 



Head-lobes of Echiurids.* — J. W. Spengel has studied the minute 

 structure of the proboscis or head-lobes of Echiurus, BonelUa, and 

 Thalassema. He deals first with the extension of the coelom into the 

 proboscis and the frenula of muscle-fibres, which forms a filter between 

 it and the trunk-ccelom. He deals in the second place with the muscu- 

 lature of the proboscis and its relation to that of the bodj-wall. 



Ganglion-cells of Lumbricidse.t — Andreas von Sziits has studied the 

 minute structure of the ganglion cells in Lumhricus terrestris, Eisenia 

 rosea, and Helodrilns {De?idrobaena) platyurus. He finds that among 

 the cells with the well-known neurofibrillar structure there are some in 

 which the efferent and afferent fibrils enter by the same jfrocess, and 

 which show a neurofibrillar framework divided into a perisomal and a 

 perinuclear framework with radiating threads between. These corre- 

 spond to a type which Apathy described in the leech. The author dis- 

 tinguishes in all three types in the earthworm : — (J.) pear-shaped cells 

 with one process or with two, with a uniform neurofibrillar framework ; 

 (2) multipolar motor cells, which, like the preceding, have their equiva- 

 lents in Vertebrates : and (3) pear-shaped unipolar cells, as above 

 mentioned, with distinct perisomal and perinuclear framework. 



Nematohelminthes. 



Fertilization Phenomena in Ascaris megalocephala.J — 0. Zach- 

 arias maintains that a remarkable fusion (cryptosymmixis) of the 

 chromatin of the spermatozoon with that of the ovum probably occurs 

 in the first two blastomeres, and recurs at the end of each telephase (i.e. 

 in all the resting stages of the nuclei) until a perfect equilibrium between 

 the two sets of sex-affinities is established. For this and for other 

 reasons, e.g. the continuous chromatin coil in the pronuclei and in the 

 blastomere nuclei, Zacharias strongly opposes the theory of the persistent 

 individuality of the chromosomes. Special attention is directed to the 

 theloid (or teat-like) appearance of the blastomere nuclei. The majority 

 show four teat-like processes, usually in the division-plane. 



Parietal-cells in Gonads of Ascaris megalocephala.§ — E. Faure- 



Fremiet finds it probable that the parietal cells of the reproductive 

 organs in this Nematode have the same origin as the germinative cells 

 proper. This conclusion is suggested by the observations of Leuckart 

 and of Wasielewski. But the mitoses of these parietal cells are quite 

 distinctly of the somatic type. It seems therefore as if the primitive 

 germ-cells gave origin to germinative cells proper and at the same time 

 to cells which are somatic as regards their chromosomes and as regards 

 their function. 



* Zeitschr. wiss. Zool., c. (1912) pp. 342-85 (4 pis. and 3 figs.), 



t Anat. Anzeig., xlii. (1912) pp. 272-9 (4 figs.), 



t Anat. Anzeig., xlii. (1912) pp. 353-84 (13 figs.). 



§ Bull. Zool. Soc. France, xxxvii. (1912) pp. 273-4. 



