706 SUMMARY OF CURRENT RESEARCHES RELATING TO 



or summer of the third year. In lower lying regions the embryos may 

 be born late in the summer of the second year of gestation. In Alpine 

 regions some of the embryos of the same year may not be born till the 

 fourth year of gestation. The Alpine salamander has thus, at least in 

 the higher parts of its range, a longer period of gestation than that 

 occurring in any other known animal. In mountainous regions a year 

 passes between the end of gestation and the liberation of fresh ova. 

 S. atra thus usually completes its reproductive cycle in three years, sc 

 that about a third of the females will reproduce each year. 



Various anomalies connected with reproduction were "found. At 

 ovulation the ovaries sometimes liberate bladder-like structures, which 

 may be met with both in the abdominal cavity and in the oviduct. The 

 discrepancy between the maturing of the two ovaries was sometimes so 

 great that ovulation from both could hardly take place in the same year. 

 Anomalies in the contents of the uterus were also found. Sometimes 

 two embryos were found within a single envelope, and it is probably to 

 this anomaly that the occasional occurrence of two older embryos in one 

 uterus is to be referred. In regard to anomalies already known the 

 author's results differ somewhat from those of previous observers. 

 Differences in size between embryos in the later 'stages, leading to 

 discrepancies in the time of birth, arise, he finds, only during the course 

 of development of embryos of the same age ; dead embryonal ova are 

 never replaced by nutritive ova. Abnormal embryos, whether occurring 

 alone or along with normal ones, always arise from embryonal ova. 



The embryonal ovum is distinguished from the nutritive ovum by 

 the presence of a strong, thick, gelatinous envelope ; the nutritive ovum 

 has occasionally a very thin envelope, but is more often without any. 

 There is never even a partial development of the nutritive ova. The 

 difference between the two forms is not due to any primary difference 

 in the ova, but is brought about by the peculiar conditions in the uterus. 

 Fertilisation takes place within the caudal portion of the uterus. The 

 chief cause of the breaking down of the nutritive ova is mechanical, and 

 is conditioned mainly by the movements of the emerging embryo. 



In regard to phylogeny, Wunderer's observations lead him to 

 regard the Alpine salamander as a direct descendant of an egg-laying 

 Urodelan type with internal fertilisation. 



Parthenogenetic Segmentation in Hen's Eggs. — A. Lecaillon* 

 has studied this in the case of hens which have not been mated or which 

 have been separated from a cock for a long time. Nucleated cells 

 are seen and stages of karyokinesis. The cells and the nuclei vary 

 much in size, and the mitosis is also variable. A few hours after laying 

 no dividing cells are to be seen, but many nuclei are still visible. 

 Degeneration sets in quickly. 



The authorf also calls attention to the interesting fact that the cells 

 which arise by parthenogenetic segmentation of the eggs of the fowl 

 contain attraction spheres and centrosomes. 



* C.R. Soc. Biol. Paris, lxvi. (1909) pp. 1053-5. 

 t Comptes Rendus, cxlix. (1909) pp. 64-6. 



