256 SUMMARY OF CURRENT RESEARCHES RELATING TO 



genesis of nerve is whether or not there exists previous to nervous 

 (neurofibrillar) connexion between neural tube and myotome a connexion 

 by means of undifferentiated protoplasmic threads or plasmodesmata. 

 In embryos of Sqiiahis, previous to the stage of 4*5 mm., there are no 

 protoplasmic connexions between tube and myotomes. Neurofibrillar 

 substance is present in the primary connexion between tube and 

 myotome. Within the plasmodesmata of Paton and Held may be found 

 in adequately stained Bielschowsky-Paton preparations deeply stained 

 neurofibrils which may be traced to bipolar neuroblasts within the 

 neural tube. The assumption of the Hertwigs, later supported by 

 Paton and Held, that neuromuscular connexions are primarily effected 

 by indifferent cells, and that the " plasmodesmata " thus formed are 

 utilized as " paths *' by the growing neuraxones, does not accord with 

 the observed facts. ■ J. A. T. 



Influence of Sea-water on Myotomes and Heart of Dog-fish 

 Embryos. — P. AVixtrebert {Comptes Rendus Soc. Biol., 1020, 83, 

 1391-4). Sea-water or any saline solution different from the peri- 

 embryonic fluid (of Scylliorhmus canicula) affects the reactions of the 

 embryo, the influence differing according to the presence or absence 

 of lesions in the skin. The musculature is unequally affected, for in 

 aneural embryos with torn ectoderm the heart continues to beat while 

 the myotomes are arrested. At different stages of development the 

 skeletal movements are variably affected ; the neuromuscular functioning 

 continues in conditions in which the aneural contraction has stopped. 



J. A. T. 



Heredity of Twin Births.— C. B. Davenport {Proc. Soc. Exper. 

 Biol, and lUed., 1020, 17, 75-7). About 1 p.c. of human births are 

 twin births. But there are certain families in which the proportion 

 rises to 5, 10, or even 15 p.c. There can be little doubt that, as in 

 sheep, so in man, there are sti*ains having a special tendency toward the 

 production of twins. Twinning is due not merely to double ovulation, 

 but upon such a quality of sperm as shall result in a high proportion of 

 fertilization of eggs ovulated and a small proportion of fertilized eggs 

 containing lethal factors. J. A. T. 



Carunculi in Uterus of Sheep and Goat. — Ed. PcETTerer and 

 S. Y oiio:so¥F {Co mj-ttes Rendus Soc. BioJ., 1021, 84, 187-90). If an ovary 

 is grafted into the cavity of the uterus, after removal of the ovaries, 

 carunculi appear. They are of connective tissue origin, they are hyper- 

 trophied, they become vesicular, and they disappear with the caduca. 

 Where there is little caduca, as in Ruminants, the cells in question 

 persist and are transformed into connective or epithelial cells. They 

 might be called pulp-cells. A hormone from the engrafted ovary 

 stimulates the formation of an epithelial syncytium in the uterine glands. 

 The deeper portion is transformed into pulp-cells, which persist and 

 take part in the reconstitution of the uterine mucosa. A more superficial 

 portion of the pulp-cells may undergo retrogression cind disappear. 



