/.OOLOGY AND BOTANY, MICROSCOPY, ETC. 707 



The same differences were found to be manifested by the offspring of 

 the warm-room and cold-room parents, although the animals belonging 

 to the second generation were all reared together in a common room, 

 and exposed to identical temperature conditions. In the experiment in 

 question there were 141 of the warm-room descendants, and 145 of the 

 cold-room descendants. The differences between the two sets were 

 revealed not only through a comparison of the gross averages of the 

 three characters in the two contrasted sets of individuals, but by a 

 comparison between averages computed for each group, when the mice 

 have been divided into groups according to size, and when these groups 

 have been still further divided according to sex. By calculations of 

 probability it has been shown that the chances for the purely " acci- 

 dental " occurrence of all these variations are very slight. These differ- 

 ences among the offspring were manifested with fullest certainty in an 

 early series of measurements, made at the age of 6 weeks. In a later 

 series, made at the mean age of :>A months, the same relations were 

 found to exist, though in a less striking degree. The differences are 

 exhibited with a closer approach to unanimity by the females than by 

 the males. 



The author discusses the various interpretations to which this re- 

 appearance of the parental differences in the two sets of offspring is 

 open. Some of these — that it may be due to "accident" or "coinci- 

 dence " ; to a slight unconscious bias of the caliper measurements in 

 favour of the desired result ; to the immediate effect of temperature on 

 the germ-cells ; or to the influence of temperature during pregnancy — 

 are very briefly dismissed. But more serious consideration is given to 

 the following possible interpretations : the differences in the length of 

 the peripheral parts may be correlated with some constitutional difference 

 of a very general kind in the two sets of parents. The development of 

 one set of mice may have in some way been retarded or accelerated 

 relatively to that of the other. Though temperature as such may not 

 directly affect either germ-cells or foetus, it may have, even on the body 

 of the parent, an indirect influence due to the formation of specific 

 chemical substances, which, through the blood, might influence both body 

 and germ-cells. Finally, changes undergone in the parent body may 

 themselves be registered in some way in the germ-cells so as to be 

 repeated in some measure in the next generation. The author inclines 

 to think that the truth will be found to lie in one or both of the last 

 two alternatives, but he maintains that no decisive verdict can be given 

 until a sufficient number of experiments to test every possible hypothesis 

 have been carried out. This work he hopes to be able to undertake in 

 the near future. 



Full details of the results of the present set of experiments are 

 appended to the paper in tabular form. 



b. Histology. 



Nucleated Red Blood Corpuscles in Blood-vessels of the Hypo- 

 physis.* — Alezais and Peyron describe nucleated elements in the 



* C.R. Soc. Biol. Paris, lxix. (1910) pp. 204-6. 



