22 SUMMARY OF CUKRENT RESEARCHES RELATING TO 



epithelium regresses, near some of the latter in the regression of the 

 layer of connective tissue, although in this respect the analogy is not 

 complete." 



Development of Peripheral Nerves.* — R. G. Harrison has made a 

 number of experiments on frog larvse, and comes to the following 

 conclusions. The axis cylinder of the nerve-fibre is the outgrowth of a 

 single ganglion-cell, with which it remains in continuity throughout 

 life. It grows gradually from the centre towards the periphery, 

 establishing secondary connection with its end organ. The other 

 elements, the cells of Schwann, which are found upon the developing 

 uq^'ve, have nothing to do with its genesis, though they may play an 

 important part in the nutrition and protection of the fibres. 



Development of Human Cerebellum.f^L. Bolk notes, inter alia, 

 that in the grooving of the human cerebellum two stages may be 

 observed : in the first stages those grooves arise that in general are 

 characteristic for the mammalian cerebellum, in the second stage those 

 grooves become visible that are typical for the cerebellum of the Primates. 

 The cerebellum of the Primates, as compared to that of the other 

 Mammals, is characterised by a progressive development of the anterior 

 and middle zones and a regression of the posterior zone. The facts of 

 development suggest that the cortex of the cerebellum is not an organ 

 with an homogeneous distributed function, but a well-organised entirety 

 with localised functions. 



Development of Pancreas in Alytes obstetricans.J — W. Braun has 

 followed this, and finds tliat the pancreas arises from the undifferentiated 

 cells of the yolk-mass, on the border of the anterior part of the yolk-gut. 

 There are three primordia, a dorsal and two ventral ; the dorsal arises 

 first, the others later. The three fuse, first the right ventral with the 

 dorsal, then the left ventral with these. The whole development up to 

 the time of fusion is completed while the larva grows about 1 mm. 

 (4 "5 mm. to 5"."> mm.). Tlie pancreas-cells, which are formed from the 

 primitive yolk-cells massed on the yolk-gut, become transformed into 

 epithelial gland-cells only after fusion of the primordia. Active cell- 

 multiplication by nuclear division takes place in all three parts equally, 

 and the organ thus increases in size. The tubular character of the gland 

 is developed gradually from the centre to the periphery, so that in the 

 later stages the marginal portions show an arrangement of compactly- 

 arranged cells. In the adult animal the organ lies in the concavity of 

 the gastro-duodenal loop. 



Weight of Hen's Eggs.§ — E. Schein comments on the very variable 

 size and weight of the eggs of the common fowl. Some bantam eggs 

 weighed 30-35 grm., while those of Spanish hens weighed 70-75 grm. 

 Seven weighed 1 lb. The average of 165 Thnringian fowls' eggs 

 (weighed by Dr. Lenz-Schnepfental) was 62 grm. The author reports 



• Amer. Journ. Anatomy, v. (1906) pp. 121-31 (5 figs.). 



t Proc. Section Sciences K. Akad. Amsterdam, viii. (1905) pp. 85-91, 



X Morphol. Jahrb., xxxvi. (1906) pp. 27-51 {2 pis.). 



§ Jahresb. Ges. Nat. Gera, Ixvi-lxviii. (1906) pp. 179-80. 



