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ANIMAL BIOLOGY. 



Agnes M. Claypole. 



Separates of papers and books on animal biology should be sent for review to 



Agnes M. Claypole, Sage College, 



Ithaca, N. Y. 



CURRENT LITERATURE. 



The author started in the study of this 

 Beard, J. D. Functions of the Thymus. Lan- 11 .• i 1 



cet p. I Jan. i8qg. problematical organ several years ago, 



and has but now reached conclusive 

 results. His subject was Raia batis the smooth skate. At the period when 

 leucocytes first appear there are no lymphoid structures of any kind, but the 

 primordia of the thymus are present and from their epithelial cells the first leuco- 

 cytes are formed. When the embryos are about 28 mm. and upward in length, the 

 thymus sets to work in earnest to form leucocytes, and these wandering cells 

 begin to emerge in crowds causing larger or smaller "breaks" on the contour 

 of the thymus. 



It is KoUiker, who showed that leucocytes arise in the thymus from its origi- 

 nal epithelial cells. GuUand observed that the first leucocytes formed are found 

 in the mesoblast near the thymus. Now Dr. Beard has shown that the first leuco- 

 cytes arise in the thymus from its epithelial cells and that thus it is the parent 

 source of the leucocytes of the body. a. m. c. 



Grassi, B., Bignami, A. and Bastianelli, 0. Mos- The authors come to the conclusions 

 quitoes and Malaria. Atti. R. Accad. Lincei that the Haemosporidia or Haemamoe- 

 (Rend.), 8: 21-8, 1899. ,. • , , , 



bmae pass m man through a chapter of 



their life cycle characterized by the long duration of the amoeboid phase and 

 the absence of the encapsulated stages. It is undetermined how many times 

 they reproduce, but they also give rise to forms which are sterile in man. The 

 last stage reaches the intestine of the adult Anopheles daviger Fabr. and develops 

 as typical sporozoa forming an enormous number of sporozoites which accu- 

 mulate in the salivary glands and return to man when the mosquito punctures 

 the skin. It is claimed to be a demonstrated fact that the parasites pass directly 

 from man to mosquito and from mosquito to man, but other species of Diptera 

 besides Anopheles daviger may also share in the dissemination, and the open 

 question of passage from the parent insect to its offspring is left undiscussed. 



A. M. c. 



