177 



SUMMARY OF CURRENT RESEARCHES 



RELATING TO 



ZOOLOGY AND BOTANY 



(principally invertebrata and cryptogamia), 



MICROSCOPY, Etc.* 



ZOOLOGY. 



VERTEBRATA. 



a. Embryolog-y. f 



Germ-Cells of Armadillo.^ — Aimee S. Vanneman has studied 

 the germ-cells of Tatuski novemcincta, and finds that they are conspicu- 

 ously large, and first discernible along the endodermic wall of the 

 blastocyst, just preceding the primary bud-stages. They are extremely 

 few in number. The active, embryonic germ-cells, however, probably 

 do not arise until the time of the secondary bud-stage, appearing in the 

 vicinity of each of the four embryonic areas. 



During early primitive streak stages germ-cells are seen dividing, 

 previous to pushing a way into the endoderm of the future gut region. 

 After gaining entrance into the gut endoderm, the germ-cells are carried 

 in the thickening intestinal wall as, during the somite stages, it rounds 

 up to form a closed tube. By the time the embryo has attained a length 

 of 4 mm., and has a pronounced cervical bend, the germ-cells may be 

 seen in the act of leaving the ventral, intestinal wall to enter the 

 surrounding mesenchyme tissue. They are amoeboid. 



In embryos of 5 and 6 mm., the germ-cells appear at the base of 

 the well-developed mesentery, usually not below the level of the three 

 blood-vessels of that region. They are also present in the loose mesen- 

 chyme under the aorta, and en route to the germinal epithelium which 

 has not yet thickened. 



In the 10 mm. embryo the germ-cells are established in the indifferent 

 gonad. They are slightly enlarged, preparatory to division. 



A study of early stages suggests that germ-cells may arise from 



* The Society does not hold itself responsible for the views of the authors 

 of the papers abstracted. The object of this part of the Journal is to present 

 a summary of the papers as actually published, and to describe and illustrate 

 Instruments, Apparatus, etc., which are either new or have not been previously 

 described in this country. 



t This section includes not only papers relating to Embryology properly so 

 called, but also those dealing with Evolution, Development, Reproduction, and 

 allied subjects. 



♦' Amer. Journ. Anat., xxii. (1917) pp. 341-63 (3 pis. and 2 figs.). 



