SUMMARY OF CURRENT RESEAKCHES. 147 



Significance of Sperm-bundles.*— E. Bugnion and N. Popoff point 

 out that a sperm-bundle (spermatoblast) results from the proliferation 

 of a single initial cell, which lias itself arisen from the division of a 

 primitive germ-cell. This proliferation, which proceeds in regular 

 geometrical progression, leads to the production of a definite number of 

 elements in each bundle — a number typical for the species, or, it may 

 be, to a multiple of this number. Each bundle is associated with a 

 cytophore, or nutritive cell, which secures the coherence of the elements, 

 supports them, and nourishes them. The nutritive cell arises from the 

 germinal epithelium, but the differentiation of this cell, separated at an 

 early stage from the corresponding spermatic cell, does not affect the 

 typical number of elements in the bundle. The initial spermatic cell 

 corresponds to a primordial ovum, and the nutritive cell to an epithelial 

 cell of the ovarian follicle. 



Fasciculation of Spermatozoa.f — G. Loisel continues his investiga- 

 tion of the fasciculation of spermatozoa in the testes. He has studied 

 the subject in mammals, birds, reptiles, and amphibians. It appears 

 that the orientation of the spermatozoa is due to the secretion of 

 glandular cells in the parietal layer of the seminiferous epithelium, and 

 of Sertoli's cells in particular. There is a marked chemotactic influence. 

 There may also be (1) a mutual influence among the spermatozoa 

 themselves ; (2) an influence due to agglutinating substances ; and in 

 some cases (3) a mechanical influence of pressure. 



Influence of Molluscan Spermatozoa on Ova of Sea Urchins.J — 

 Hans Kupelweiser finds that the ova of Strongylocentrotus purpuratus 

 and S.franziscanus can be made to develop if treated with spermatozoa 

 of Mytihis. Sometimes 50 p.c, sometimes 70 p.c. of the eggs '• de- 

 veloped." They formed no membrane, but segmented like those 

 illustrating artificial parthenogenesis. In some cases gastrulae with 

 mesenchyme cells were formed. When more concentrated sperm-fluid 

 was used, the eggs formed a membrane. Even with dead sperms or 

 filtrate of sperms, a membrane was formed, but only in about a fifth of 

 the sea-urchin ova. After a membrane had been formed the eggs did 

 not develop when exposed to mussel spermatozoa. It seems that the 

 sperms must come into actual contact with the ovum. In some cases, 

 the experimenter found a spermatozoon or several within the ovum, and 

 the two nuclei surrounded by a common radiation. Confirmation by 

 other observers will be looked for with interest. 



Gastrulation in General and in Mammals in Particular.§ — 

 A. C. F. Eternod gives an account of the gastrula stage in representative 

 types, and discusses the question of gastrulation in Mammals. He 

 maintains that in man, as in all " deutolecithal " vertebrates, the embryo 

 appears at the expense of the dorsal portion of a primitive gastrula, 

 which subsequently forms by successive budding a linear series of 

 secondary gastrulae, giving origin to the metameres. 



* Arch. Sci. Phys. Nat., xxii. (1906) pp. 497-500. 



t Journ. de I'Aiiat. Physiol., xlii. (1906) pp. 541-66 (2 pis. and 9 figs.). 



X Biol. Centralbl , xxvi. (1906) pp. 744-8. 



§ Bull. Soc. Vaudoise Sci. Nat., xlii. (1906) pp. 197-224 (6 pis. and 16 figs.). 



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