ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 935 



Spermatogenesis in Amphibians.* — Prof. v. la Valette St. George 

 reports the result of his investigation of the ontogeny of the sperma- 

 tozoa in gome Amphibia. 



In Bufo cinerens he reasserts what he maintained some years 

 previously, that the tail consists not of one spiral fringe, but of two 

 filaments united by a thin membrane. The addition of reagents 

 effects the separation of the two tail filaments. The movements of the 

 sperms are described. The fate of the residue of the spermatide not 

 used up in forming the sperm is noted, but no new fact of importance 

 is announced. In regard to Hijla arborea and Bana esculenta, several 

 descriptive notes are communicated, and the validity of former con- 

 clusions is in some particulars corroborated. The accuracy of the 

 author's long-since stated law of spermatogenesis is vigorously em- 

 phasized. 



History of the Primitive Streak.f — Prof. J. Kollmann gives an 

 account of the history of the so-called primitive streak in "mero- 

 blastia." Seen from the surface, the blastoderm exhibits three primi- 

 tive organs: (1) the peripheral ridge, (2) the primitive streak, (3) the 

 medullary groove and ridges. In the bird, the peripheral ring of 

 blastoderm which marks the beginning of the area opaca first appears, 

 then the primitive streak in the enclosed space, then the resulting 

 primitive groove and folds, and, lastly, the medullary groove and 

 ridges without any association with the primitive streak. So it is 

 in mammals, though the peripheral pad is not so thick, and more 

 transitory. 



Kollmann notes as characteristics of the primitive streak (1) that 

 it is associated with the peripheral ridge, (2) that it is at first closed 

 in front, (3) that the subsequent primitive folds are also in association 

 with the peripheral ridge, (4) that the primitive streak goes to form 

 the posterior portion of the trunk, and (5) that though the chorda 

 dorsalis is associated with it in position, it does not arise from it. 



In the Selachian development the following facts may be ob- 

 served: — The primitive streak is (I.) at first sickle-shaped in the 

 posterior region of the blastoderm ; it afterwards (II.) exhibits a 

 median thickened portion, peripheral bud, and two sickle-shaped 

 horns ; from the median thickened portion the primitive groove 

 results (III.), intruding into the area pellucida, as in birds and 

 mammals ; the folds elongate backwards, following the posterior 

 margin of the germinal disc, and forming finally the caudal portion 

 of the body. The primitive groove of the III. stage ought not to be 

 termed the medullary groove, from which it is quite independent. 



In regard to Teleostei, Kollmann refers to the primitive streak, 

 the peripheral bud, the sickle-shaped streaks, associated posteriorly 

 with the peripheral ridge, and a small region of embryonic shield 

 lying in front of the peripheral bud. 



A slight transitory constriction of the peripheral bud represents 



* Arch. f. Mikr. Anat., xxvii. (1886) pp. 385-96 (3 pis.). 

 t Biol. Centralbl., vi. (1886) pp. 314-9 (Bench t Versamml. Deutsch. Natm-f'., 

 Strassburg, 1885). 



