ERYTHROBLASTS IN THE PIG EMBRYO 179 



dence, referring to the erythroblasts in the blood of spermophile 

 and pig embryos states that 



De leur cytoplasm se detachent de petits morceaux qui fournissent les 

 globules rouges definitifs, ou plastides lesquels en circulant dans le sang 

 s'impregent plus fortement d,hemoglobine. On rencontre aussi de 

 plus grands fragments de cytoplasma depourvus de noyau mais colores 

 par hemoglobine. Ce sont les debris d' erythroblastes dont le noyau, 

 entoure d'un peu de protoplasma, s'est detache, formant ansi quelque- 

 fois les soi-disant 'noyoux lil^res', en realite de petites cellules ayant tres 

 peu de cytoplasme. Ce cytoplasme anuclee conserve sa taille primitive 

 on bien se brise de nonveau en produisant des globules plus petits (p. 280). 



Howell ('91), who has strongly supported the nuclear extrusion 

 view, records an observation on the bone marrow of the cat which 

 is especially interesting in relation to the present subject. He 

 says : 



In several instances, when examining the marrow, I have met with 

 appearances which seemed to justify Malassez's theory. Nucleated red 

 corpuscles were seen with one or more non-nucleated corpuscles ap- 

 parently budding out from them .... I was at first inclined to 

 believe that we must admit that, under certain circumstances at least, 

 new red corpuscles may be produced by budding in the way described by 

 Malassez (p. 104). 



In a summation of his discussion he concludes, however, that 

 "the apparent gemmation of non-nucleated red corpuscles from the 

 nucleated forms, as observed by Malassez, is probably owing to 

 the multiplication of the nucleated cell and the subsequent loss of 

 a nucleus from one or more of the daughter-cells before the com- 

 plete separation of the cells has been effective" (p. 113), Being 

 convinced of the correctness of nuclear extrusion, he states, "the 

 explanation that I have adopted seems to me to be preferable 

 to supposing that in the marrow new blood corpuscles are formed 

 from the same cells by two entirely different methods of repro- 

 duction" (p. 104). In an examination of Howell's figure one can- 

 not fail to be impressed with their resemblance to some of the cell 

 forms observed in the present study of the pig embryo in which 

 it was of course possible to ascertain that the cytoplasmic portion 

 which was being constricted off from the cell had at no time con- 

 tained a nucleus. 



