180 SUMMARY OF CURRENT RESEARCHES RELATING TO 



monophthalmia asymmetrica, and anophthalmia), the ear-vessels, the 

 olfactory pits, the mouth, the central nervous system, the heart and 

 blood-vessels, the fins, and the form of the body. 



A condition of hydrops was found in many embryos, due, apparently, 

 to blood vascular abnormalities which might be considered as homo- 

 logous with some forms of hydrocephalus in man. In many eggs 

 parts of the embryonic material were destroyed, while the residue 

 developed into anterior hemi-embryos or other meroplastic embryos. 

 In some eggs one eye developed from a small fragment of a medullary 

 plate independently of an embryo. 



As to the mode of action of butyi'ic acid and acetone, it is suggested 

 that a process of blastolytic fragmentation is in some cases induced. 

 Regarding the formation of the various degrees of the " cyclopean " 

 defect, it is concluded that the fusion theory of Speeman and Lewis is 

 justified in the main. An additional assumption is made, namely, that 

 the blastolytic process which ehmiuates parts of the potential interocular 

 or ophthalmoblastic material takes place at a very early stage of develop- 

 ment, i.e. before the formation of the embryonic shield. The results 

 obtained tend to justify the assumption that monstrous development 

 may be due to metabolic toxaemia. 



Reproduction of White Rat.* — Helen Dean King and J. M. 

 Stotsenburg note that breeding extends throughout the year in 3Ius 

 norvegkus albimis, though the periods of greatest sexual activity are 

 in spring and autumn. The sex ratio in 1,089 litters was 107 '5 males 

 to 100 females. There is apparently a seasonal variation in the sex 

 ratio, for it is relatively low in litters cast in spring and early autumn, 

 much higher in those cast in summer. Data for 75 litters produced by 

 21 albino females indicate that the sex ratio among the first offspring 

 of young females is higher than among the offspring of the same 

 females when they are' at the height of their reproductive power. 



There does not seem to be any relation between the size of a litter 

 and the sex of its members. The average for 1,089 litters was seven, 

 lower than for grey rats, higher than for black rats. There is no pro- 

 nounced seasonal variation in the size of the litter comparable to the 

 seasonal variation noted in the sex ratios. As a rule the first of an 

 albino female's four litters is the smallest, the second and third are the 

 largest, and the fourth is a little larger than the first. 



Growth of the FoBtal Albino Rat.f — J. M. Stotsenburg has 

 studied this on fresh specimens. Lowrey's study of the pre-natal 

 growth of the pig and Jackson's study of human growth were based on 

 preserved material. The rat fcetuses studied were all from second 

 litters, normal behaviour having been exhibited in the first litter. The 

 foetus of thirteen days was found to be the youngest which would stand 

 manipulation without damage, and the observations began with that 

 age. They continued to the twenty-second day — about the time of 

 birth. Thirty-three females were studied and 330 foetuses weighed. 



* Anat. Record, ix. (1915) pp. 403-20 (1 fig.), 

 t Anat. Eecord, ix, (1915) pp. 667-82 (2 figs.) 



