SUMMARY OF CURRENT RESEARCHES 



RELATING TO 



ZOOLOGY AND BOTANY 



(principally invertebrata and cryptogamia), 



MICEOSCOPY, Etc.* 



ZOOLOGY. 



VERTEBBATA. 



a. Embryologry.t 



Eggs and Egg-envelopes of Selachians.l — H. Braus describes the 

 eggs and egg-envelopes of Hexanchus griseus, Heptanchus cmereus, 

 Spincix niger, Acanthias hlainvillii, Centrophorus granulosus, and other 

 forms. He also discusses the Hght which certain embryonic features, 

 e.g. the external gills, throw on the relationships of Notidanidse and 

 Spinacidse. 



Development of Heart and Chief Blood-vessels in Megaloba- 

 trachus maximus.§ — Petronella Johanna de Rooy has reached the 

 following conclusions. The pericardium is formed one day before the 

 heart, as a cavity between splanchnopleure and somatopleure. The endo- 

 thelium of the heart is laid down in an embryo of twenty days as a 

 group of cells derived from the splanchnopleure. The ventral endo- 

 dermic diverticulum which has been repeatedly regarded as the matrix 

 of the cardiac endothelium is the primordium of the thyroid. The cells 

 unite to form a primitive cardiac vesicle, passing anteriorly into the first 

 aortic arches, posteriorly into the omphalo-meseuteric veins. The blood 

 is formed in the free mesodermic margin growing ventrally ; cell-walls 

 appear bounding the large corpuscles, each of which has a nucleus and 

 many yolk-pla'es. When the omphalo-mesenteric vein comes into con- 

 nection with the blood-islets, then blood-cells appear in the heart, but 

 not earlier. The blood-islets spread on each side over the whole yolk, 

 and posteriorly they unite from right and left (sub-intestinal vein). 

 The latter arises from the constriction off of several yolk-vessels, which 



* The Society are not intended to be denoted by the editorial " we," and the / 

 do not hold themselves responsible for the views of the authors of the papers 

 noted, nor for any claim to novelty or otherwise made by them. The object of 

 this part of the Journal is to present a summary of the papers as actually ptib- 

 lislxJ, and to (.escribe 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. 



X S.B. k. Preuss. Akad. Wiss. Berlin, 1906, pp. 907-32 (8 figs.). 



§ Jen. Zeitschr. Naturw., xlii. (1907) pp. 309-46 (6 pis.). 



