SUM)] A I! Y OF CURRENT RESEARCHES 



RELATING TO 



ZOOLOGY AND BOTANY 



(PRINCIPALLY INVERTEBRATA AND CRYPTOftAMIA), 



MICROSCOPY, Etc.* 



ZOOLOGY. 



VERTEBRATA. 

 a. Embryology, f 



Sex-determination in Pigs.} — 0. H. Parker refers to the hypothesis 

 of Seligson that in Mammals the right ovary gives rise to ova that 

 produce male offspring, the left to ova that produce female offspring. 

 If this were so, the pairs of embryo pigs in the part of the uterus next 

 the right ovary ought to be predominantly males and those next the 

 left predominantly females. This is not the case. Pairs of embryos 

 composed of two males or of two females occur in about the same pro- 

 portions next the right ovary and next the left. A very similar pro- 

 portion occurs at the division of the horns of the uterus. Although the 

 sex of the offspring is thus shown not to be correlated with the side of 

 the body from which the ovum that gave rise to the young came, it 

 might be supposed that in any female a given ovary would always pro- 

 duce offspring of the same sex. In that case we should expect to find 

 the great majority of pairs of young next the ovaries to be either both 

 males or both females. But there are almost as many pairs composed 

 of one male and one female next the ovaries as there are at the division 

 of the horns. It may be concluded that in the pig each ovary produces 

 ova which may give rise to either male or female offspring. For the 

 albino rat it has been shown by Doncaster and Marshall, and by King, 

 that a single ovary may give rise to ova which produce both sexes. 



Litters and Nipples in Swine.§ — G. H. Parker and C. Bullard 

 found that 1000 litters of unborn pigs contained 5700 individuals ; the 



* The Society are not intended to be denoted by the editorial " we," and they 

 do not hold themselves responsible for the views of the authors of the papers 

 noted, nor for any claim to novelty or otherwise made by them. The object of 

 this part of the Journal is to present a summary of the papers as actually pub- 

 lished, and to describe and illustrate Instruments, Apparatus, etc., which are 

 either new or have not been previously described in this country. 



t This section includes not only papers relating to Embryology properly so- 

 called, but also those dealing with Evolution, Development, Reproduction, and 

 allied subjects. J Science, xxxix. (1914) pp. 215-16. 



§ Proo. Amer. Acad., xlix. (1913) pp. 399-426. 



