Volume //.] January, 1901. [A 7 "^. ./ 



BIOLOGICAL BULLETIN. 



THE CENTROSOME IN THE MATURATION AND 

 FERTILIZATION OF BULLA SOLITARIA. 



MARTIN SMALLWOOD. 



THE material upon which the following observations were 

 made was collected at Woods Holl during the seasons of 

 1898-1900. The greater part of the work was done at the 

 Marine Biological Laboratory under the direction of Dr. E. G. 

 Conklin, and I take this opportunity of thanking him for his 

 many valuable suggestions. I also wish to acknowledge my 

 indebtedness to Dr. C. O. Whitman and Dr. C. W. Hargitt. 



A fuller account of my observations both upon the subject 

 of this paper and the cell lineage of Bulla, with a discussion of 

 the pertinent literature, will be published later. 



The sketches illustrating the mitotic changes in maturation 

 were drawn from sections stained with Heidenhain's iron- 

 alum followed by an aqueous solution of Bordeaux. In order 

 to differentiate the sperm, it was necessary to use Conklin' s 

 mixture of haematoxylin and picric acid. The sperm, there- 

 fore, has been drawn from corresponding stages and inserted 

 into these figures. 



In the interpretation and nomenclature of the centrosome 

 and sphere I have followed in the main Van Beneden. The 

 term " centrosome " will be applied to the body which occurs at 

 the pole of the spindle, etc., when that body has become differ- 

 entiated into a central corpuscle, surrounded by a clear area, 

 the medullary zone bounded by a definite wall. The body 

 occurring at the center of the aster is the central corpuscle. 



MS 



