ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 231 



author very improbable. If retarded fertilization is a fact it may 

 possibly throw light on some cases of alleged telegony. J. A. T. 



Fate of Homozygous Yellow Mice.— W. B. Kirkham {Journ. 

 Exper. ZooL, 1919, 28, 125-35, 2 figs.). The failure of breeders and 

 investigators to obtain any homozygous yellow mice and the observed 

 smaller average litters born to yellow parents suggested the advisability 

 of attacking the problem from the embryological side. All mouse- 

 embryos encounter a crisis at the time of the implantation of the 

 blastula in the wall of the uterus, and in unusually large sets of blastulte 

 one or more appear always to perish at this time without producing any 

 uterine reaction. In healthy mice other than yellows, however, those 

 blastute which induce a swelling ot the mucosa uniformly complete 

 their implantation, while the blastulte resulting from yellow matiugs 

 almost always lose at least one of each set after the mucosa has reacted. 

 Apart from this loss of certain blastulse during implantation, the 

 embryonic and early postnatal history of yellow mice is exactly the 

 same as that of mice of other coat-colours. The theory is that the 

 blastulfe lost in yellow females during implantation are the missing 

 homozygous yellow mice, and the evidence consists on the one hand in 

 the absence of any similar phenomena in healthy white mice, and on 

 the other hand in the statistical correspondence between the percentage 

 of embryos so lost and the Mendelian expectation of homozygous 

 yellows. J- A. T. 



Hereditary Tumour. — Mary B. Stark {Journ. Exper. ZooL, 1919, 

 27, 507-22, 3 pis.). Cell suspension from an " hereditary tumour " 

 in a stock .of the fly DrosophUa was injected into adult flies. Abnormal 

 growths occurred in some of the flies and caused their death. Tumours 

 were kept alive and showed further development in hanging drops of 

 Locke's solution. Tumour-cell suspension was injected into meal worms, 

 but the resistance of most of them was too great to allow the develop- 

 ment of many tumours. Only a small percentage died, and only two of 

 these had tumours visible to the naked eye. No growths occurred in 

 ordinary laboratory media. The flies were bred on sterile media under 

 absolutely sterile conditions, but the tumour continued to develop as 

 before in successive generations, and is evidently not due to a micro- 

 organism. The tumour develops in embryonic rudiments, destined to 

 develop into adult organs. Its development is initiated by excessive pro- 

 duction of melanin. ]\Ielanin occurs normally in ganglion cells, and 

 these cells are related to some of the embryonic rudiments by ganglion- 

 ated fibres. Secondary tumours or metastases occur in many of the 

 larvffi with tumours. A mutation occurred in certain flies of such a 

 kind that pigment appeared in the hypodermis cells of the ventral 

 surface of the last segment, forming a pigmented bar. It occurred only 

 in larvffi that had tumours. So far the character has not been separated 

 from the stock with hereditary tumour. J. A. T. 



Neural Plates of Chelonian Carapace.— W. J. Schmidt {Zool. 

 A'nzeig., 1916, 47, 9-13, 2 figs.). There has been considerable differ- 

 ence of opinion as to the development of the neural (and costal) plates, 



