SUMMARY OF CUERENT RESEARCHES 



RELATING TO 



ZOOLOGY AND BOTANY 



(principally invertebrata and cryptogamia) 



MICEOSCOPY, Etc.* 



ZOOLOGY. 



VERTEBRATA. 



a. Embryoloeryf 



Placoid Tooth-rudiments in Man.| — P. Adloff points out, that while 

 Mammahan teeth arise as ingrowings of the buccal epithelium into the 

 connective-tissue of the gum, the placoid teeth of Selachians arise as 

 papillae of the mesoderm growing into the epidermis. Now this placoid 

 mode of origin is known in bony fishes, Urodela, and in the crocodile. 

 Kose has seen hints of it in the human embryo. So Adloff has found in 

 a human embryo, of about nine weeks, a peculiar freely projecting epi- 

 thelial papilla lying beside a normal tooth-germ. He regards it as an 

 atavistic rehabilitation of the oldest mode of tooth-development. 



Pre-placental Nutrition in Mouse. § — J. Sobotta finds that after 

 the sixth day there is a very rapid growth of the embryo-mouse. There 

 has been almost none before this. The visceral wall of the yolk-sac 

 with its cylindrical epithelium forms by the so-called inversion a broad 

 absorption-surface, utilizing the maternal haemoglobin and other detritus 

 of the decidua cells. The gestation lasts about twenty days ; in the first 

 six there is almost no growth, but when the trophic function of the yolk- 

 sac begins the rate of growth becomes very rapid. Perhaps the whole 

 process of the inversion of the germinal layers has to do with the absorp- 

 tive function of the yolk-sac wall. 



Chromatin-reduction.l|— Emil Rohde asks the interesting question : 

 Is chromatin-diminution a general phenomenon in ripening cells or 



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

 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 

 jmblislied, 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. 



t Anat. Anzeig., xl. (1911) pp. 177-81 (4 figs.). 



§ SB. Phys.-Med. Ges. Wurzburg (1911) pp. 68-73. 



li Zeitschr. wiss. Zool., xcviii. (1911) pp. 1-30 (4 pis.). 



