RECORD OF CURRENT RESEARCHES, ETC. 



401 



that they arc so much larger, they resemble blood-corpuscles. These 

 cells destroy the spermatozoa and ova. In a testis it may be observed 

 that these cells, at various stages of development, surround the sper- 

 matoblasts ; the latter disappear and break up, and each cell takes up 

 a portion of its substance ; these now alter in appearance, cease to 

 exhibit amoeboid movements, and pass into the vas deferens. Very 

 similar phenomena were observed in the ovarian tubes of Aiilostomum; 

 the cells pass through the vitelline membrane, the yolk decreases in 

 size, and then divides ; the membrane soon becomes lost. The number 

 of ova thus destroyed is said to be greater than those which come to 

 maturity. Bacteria were observed in the vagina of Aidostomum and 

 Hirudo. 



In the Hirudinea the ova also undergo fatty degeneration ; this 

 commences at the hinder end of the ovary and gradually passes on 

 to the median portion. 



These observations afford some explanation of what has been seen 

 by various embryologists ; La Valette had noticed amoeboid cells in 

 the testes of various animals ; and Pfliiger had observed fatty degene- 

 ration in the ovary of the calf and of the cat. The nutrition of ova 

 and embryos by yolk-cells, which is so common a phenomenon among 

 the Hirudinea and Dajjhnida, may also be regarded as a case of fatty 

 degeneration. Finally, it is of interest to note that Pfliiger has 

 observed a similar destruction of rein'oductive material in the vege- 

 table kingdom. 



Theory of the OvTim.* — Dr. Brandt regards the germinal vesicle 

 as a primary cell, in contradistinction to the whole egg, and to the 

 other more complicated secondary cells which make up most of the 

 tissues of the higher animals. One argument in su])port of his view 

 is, he thinks, to be found in the existence of two kinds of elements 

 in the developing insect ovum ; the blastoderm cells and the yolk- 

 spheres. The former are regarded as exclusively derivable from the 

 germinal vesicle ; the germinal vesicle persists in some form, and so 

 makes certain the continuity of succeeding generations ; it is especially 

 distinguished by its amuiboid characters, and similar amceboid move- 

 ments obtain in fertilization. Every approximation and fusion of two 

 nucleated structures in the egg is not necessarily conjugation ; true 

 conjugation or fertilization is seen in an amceboid approximation, and 

 subs< qucnt fusion, of two murphologically eijuivaleut structures. 



Development of the Germ-layers of the Rabbit, t — In the first 

 part of the now journal of biology, whicli M. E. van Bcncdcn, in con- 

 junction with Professor van Bambeko, has just started in Belgium, the 

 naturalist first named conunences an account of his " Researches on 

 the Embryology of the Mammalia." 



As Weil was the first to show, the most opportune period for 

 investigating the characters of the mature ova is that of delivery ; 

 if, tlien, a rabbit is killed two days before this wo ought to find 

 almost ripe eggs ; and so, again, for five days. The disappear- 



• ' Arcli. Mikr. Aimt..' .wii. (18S0) \\ Sf)!. 



t ' Arcb. liiol. (Van Bciiiden), i. (18«0) p. 138 (3 j.lutcb). 



