422 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Follicles and Egg-envelopes of Belone acus.* — S. Comes has 

 studied the question of the functional nature of the follicles and the 

 differentiation of the egg-envelopes in Belone with the following results. 

 He finds that the vitelline membrane appears double in tlie mature egg ; 

 the interior portion rests upon a vitelline layer differentiated from tin- 

 rest of the vitellus. The follicle secretes at the appearance of the eggs 

 of the second category (classification of Van Bambeke) a special mucus 

 which condenses and becomes the chorion. This structure in mature 

 eggs is two-layered, the outer stratum giving rise to the filaments of the 

 egg. 



Nucleolar Dissolution.! — A. Cerbuti discusses the nucleinic nucleoli 

 which he has observed in the oocytes of Selachians and the wall lizard, 

 and in Bidder's organ in the toad. He thinks they may be associated 

 with complicated " nucleolar resolutions," such as Carnoy and Lebrun 

 have described in the nucleoli of the oocytes of Batrachians. They have 

 a short duration and are dissolved into granules, but they may give rise 

 to new nucleoli. 



Experimental Researches on Egg of Rana fusca.f — A. Brachet 

 finds that in Ranafusca the structure and constitution of the fertilised 

 egg is fixed in the sense that the germinal substance is divided sym- 

 metrically on each side of a vertical plane. This plane determines the 

 place of origin of the primitive embryonic organs. Whatever the 

 orientation of the first plane of segmentation in relation to the plane of 

 bilateral symmetry of the egg, it is maintained integrally during the 

 whole course of development. All parts and all primitive organs of the 

 embryo are built up a Vendroit and at the expense of the materials 

 fixed for them by the material and dynamic constitution of the whole 

 egg. The destiny of the first blastomeres depends in normal — and in 

 some experimental — conditions, not upon their connections or their 

 reciprocal influence, but upon the place they occupy in the unsegmented 

 egg, since on this place depends the quality of the germ material and its 

 energies. 



Motion of Spermatozoa.§ — H. Adolphi has observed the movements 

 of the spermatozoa of man, sheep, and ox, has timed the rapidity of their 

 swimming, and has noticed, as Lott did for dog, and Hensen for guinea- 

 pig, that they move persistently against the current. Thus they are the 

 better able to pass upwards from the vagina in spite of opposed ciliary 

 activity. 



Structure and Movements of Spermatozoa.|| — A. Roth argues that 

 there are mechanical reasons for the way in which spermatozoa persist- 

 ently move against a current. Even under a cover-glass, when a current 

 is induced by blotting-paper at one end, the spermatozoa all arrange 

 themselves with the head against the current. The author maintains 

 that all spermatozoa have a spiral structure which effects this orientation. 



* Anat. Anzeig., xxvi. (1905) pp. 9-17. t Tom. cit., pp. 613-22 (16 figs). 



% Arch. Biol., xxi. (1904) pp. 103-60 (1 pi.). 

 § Anat. Anzeig., xxvi. (1905) pp. 549 59 (2 figs.). 



|| Arch. Anat. Physiol. /Physiol. Abth.) 1904, pp 366-70. See Zool. Zentralbl. 

 Xll. (1905) pp. 158-9. 



