16»'» SUMMARY OF CURRENT RESEARCHES RELATING TO 



deavoured, by means of sections in different planes through the yolk sac, 

 to gain some knowledge on this subject. For example, be finds in a 

 section perpendicular to the long axis of an embryo of 5 mm., and 

 through the umbilical vein, that the perivitelline cells are transformed 

 into digestive tube cells. In cells with superficial yolk spherules fusion 

 of these is seen, and, from these, cells with vacuolated contents result. 

 The contents gradually become basophile, the inter-vacuolar spaces 

 diminish in thickness, and cells with a protoplasmic reticulum sur- 

 rounded by vacuoles form the next stage. These cells are still in 

 relation to a homogeneous vitellus. Lastly, the cells of the digestive 

 tube possess a closely reticulated basophile protoplasm. 



Comparative Anatomy of the Placenta.* — Hans Strahl communi- 

 cates an important paper on the placenta in lemurs {Galago, Pro- 

 pithecus, Lemur), in Viverra civetta and in Centetes ecaudatus. The 

 lemurs have a semiplacenta diffusa ; the civet, sl placenta zonaria simplex ; 

 and Centetes, a placenta discoidalis perforata, along with an annular semi- 

 placenta avillosa. 



Placenta of Seal.f — A. J. P. van den Broek gives an account of the 

 foetal membranes and the placenta of Phoca vitulina, which have not 

 been previously described in detail. He makes an interesting com- 

 parison between the conditions in the seal and those in dog and other 

 fissipeds, showing that the pinnipeds are as distinct in placental relations 

 as otherwise. 



Involution of Uterine Mucous Membrane in Tarsius.J — Hans 

 Strahl describes the processes of involution gone through by the uterus 

 of Tar sins spectrum during the puerperal period. These take their own 

 peculiar course, and are unlike those which occur in any of the other 

 mammals in which the history of the uterus has been carefully studied. 



Implantation of Ovum of Spermophilus.§ — J. Rejsek describes the 

 early syncytium, formed by some of the cells of Rauber's layer, which 

 effects the fixation and primary nutrition of the ovum of Spermophilus 

 citillus. The processes of the syncytium bring the ovum into close 

 connection with a fluid material, which is mainly due to maternal cell- 

 products (derivatives of the blood, plasma and serum). The implanta- 

 tion and primary nutrition are altogether apart from the subsequent 

 placentation. 



Spermatozoa of Discoglossus Pictus.|| — E. Ballowitz gives a 

 description of the remarkable spermatozoa of this amphibian, which 

 measure i\ mm. in length. 



Significance of the Nucleolus in the Maturing Ovum. If — Konrad 

 Guenther has studied this problem in sea-urchins and holothurians. He 

 finds that the nucleolus is a drop secreted from the nuclear framework, 



* Abh. Senckenberg Nat. Ges., xxvii. (1904) pp. 263-319 (10 pis. and 1 fig.). 

 t K. Akad. Wetenschappen Amsterdam (Proc. Sect. Sci.) vi. (1904) pp. 610-9. 

 % Op. cit., vi. (1903) pp. 302-5. 

 5 Arch. Mikr. Anat., lxiii. (1903) pp. 259-73 (1 pi.). 

 || Tom. cit., pp. 343-64 (1 pL). 

 i Zool. Jahrb.. xix. (1903) pp. 1-28 (1 pi.). 



