24 sim MARY OF CURRENT RESEARCHES RELATING TO 



Artificial Insemination in Mammals.*— J. J. IwanofiE discusses 

 the experiments, sometimes successful, which he and others have made 

 in the artificial insemination of sheep, cows, and mares. He notes, inter 

 alia, that the seminal fluid of hybrids of horse and zebra contains no 

 spermatozoa, that the sperm may be kept successfully in weak solutions 

 of sodium chloride and carbonate, and that the spermatozoa show great 

 resisting power against cold, alcohol, and other untoward conditions. 



By artificial insemination Iwanoff made a hybrid between a female 

 white mouse and a male white rat. The hybrid was very large. 



Gastrulation in Petromyzon.f — S. Hatta describes this process in 

 considerable detail. Amongst others he emphasizes the following 

 peculiarities. Blastulation and gastrulation overlap each other to a 

 great extent in the period of their occurrence. The prime cause of this 

 belated mode of development is indisputably due to delay of segmenta- 

 tion on account of an enormous accumulation of yolk within the ovum. 

 " Concrescence " has not been detected at any stage. The macrospheric 

 hemisphere has an activity of its own. " This is an important factor in 

 bringing about the gastrulation in Petromyzon. That such is the case 

 in the Petromyzon ovum, which contains a much larger quantity of yolk 

 than the frog's ovum, and that there is no yolk plug in the former, are 

 very striking facts." To explain this the author assumes that the frog's 

 ovum is secondarily holoblastic, as has already been maintained by 

 Mitsukuri. 



Determining Factors in Metamorphosis of Anura.$ — P. Wintrebert 

 deals with the bearing of pulmonary respiration on this problem. He 

 finds that in tadpoles of Rana temporaria artificially prevented from 

 exercising this function, metamorphosis is not prevented, although it is 

 delayed. The want of the exercise of the lungs does not prevent their 

 development. At the end of transformation larva?, which up till then 

 have not breathed by their lungs, when transported into open water do 

 not try by taking in surface-air to remedy the asphyxia caused by the 

 atrophy of the branchiae. In particular, when their fore-limbs have no 

 support they do not try by hind-limb movements to keep their heads 

 above water. The absorption of the tail is more complete if the water 

 is abundantly renewed. The tadpoles of R. temporaria die in the same 

 current in which Alytes obstetricans metamorphoses and survives. In 

 this latter form cutaneous respiration in an aquatic medium suffices for 

 blood aeration. 



Experiments with Tadpoles. §— P. Wintrebert finds that lame of 

 Rana temporaria, transported from water to air, undergo precocious 

 metamorphosis. The gills and tail atrophy, being useless. The para- 

 lysed tail becomes a mere skeleton, but keeps its form. It seems that 

 the abnormal degeneration of the gills and the tail, and the precocious 



* Arch. Sci. Biol., xii. (1907) 135 pp., 6 figs. See also Zool. Zentralbl., xiv. 

 (1907) pp. 603-4. 



t Journ. Coll. Sci. Univ. Tokyo, xxi. (1907) Art. 2, pp. 1-44 (3 pis.). 

 % C.R. Soc. Biol. Paris, lxii. (1907) pp. 1154-6. 

 § Op. cit., lxiii. (1907) pp. 403-5. 



