562 SUMMARY OF CURRENT RESEARCHES RELATING TO 



itself. The reason why this pancreatic tissue appears in the papilla 

 minor rather than in the papilla major, appears to be that while the 

 ductus Santorini does not undergo a change of position during develop- 

 ment, the ductus Wirsungianus does. The papillae themselves appear 

 when the fibres of the intestinal musculature become obvious, and their 

 growth results mechanically from the increase in length of the contained 

 ducts. 



Germinal Cells of Spinal Cord.* — Prof. G. Sclavunos notes that 

 while His supposed the round cells of the developing spinal cord to 

 be special cells and the forerunners of the nerve-cells, others (e. g. 

 v. Kolliker and Schaper) regarded these cells (the germinal cells of 

 His) as the forerunners of both nerve-cells and glia-cells, and as merely 

 young un specialised epithelial cells. As the formation of the neuroglia 

 occurs during the later period of development, the question should be 

 solved by finding whether or not these cells persist after the formatiou 

 of the nerve-tissue. The author studied late embryos and new-born 

 young of dogs, cats, and mice, and finds that the elements of the spinal 

 cord go on dividing until after birth, and that His' germinal cells do not 

 disappear from the white substance with the formation of the nerve- 

 cells, but persist until birth as formative material. These germinal 

 cells occur at the point of entrance of the posterior root, in the posterior 

 root itself, and in the spinal ganglia of new-born mammals. The author 

 further finds that nerve-cells occur in the arachnoids, where they have 

 not been previously described. 



Sexual Kineses in Tritonf — Prof. J. A. Janssens finds that there 

 is a very remarkable analogy between the divisions which occur in the 

 formation of the spermatozoa in Triton and those which occur in the 

 formation of pollen-grains as described by Gregoire for the lily.+ He 

 finds that in the two sexual kineses of the spermatocytes of Triton, the 

 four rods which arise from each primitively single chromosome originate 

 by two longitudinal divisions. After the synapsis the nuclear thread 

 divides into twelve blocks, and the result of the two longitudinal 

 divisions is to convert each of these blocks into a quaternary group, the 

 latter process following immediately on the former. In the details of the 

 process the author finds a remarkable resemblance to the conditions in 

 the lily. 



Another Hermaphrodite Frog.§ — Mr. R. C. Punnett describes a 

 case in which the right side showed a well-developed Miillerian duct, a 

 ureter with a seminal vesicle, a well-developed testis, on it a pigmented 

 patch with one normal ovum ; while the left side had a well-developed 

 Miillerian duct, a small seminal vesicle, and an unmistakable ovary, with 

 an almost isolated patch of testicular tissue including spermatozoa and 

 one ovum. The fatty body was well developed on each side, and the 

 male glandular enlargement of the first finger was well marked. 



Dentition of Eodents.|| — Elin Cederblom has investigated the pro- 

 blem of replacement in the teeth of Rodents. In those with more than 



* Anat. Anzeig., xvi. (1899) pp. 467-73 (5 figs.). 



t Op. cit., xvii. (1900) pp. 520-4 (10 figs.). 



t Of. this Journal, 1899, p. 498. 



§ Ann. Nat. Hist, vi. (1900) pp. 179-SO (1 pi.). 



|| Zool. Juhrb. (Abth. Sy&t.), xiii. (1900) pp. 269-86. 



