104 \V. M. SMALLWOOD. 



instances ova containing two nucleoli (Fig. 4) were found. The 

 nncleolus is large and when mitosis begins has undergone a 

 transformation similar to the changes described for Haininca 

 (Smallwood, '05). This would indicate that the nucleolus breaks 

 up and does not take an active part in division. Furthermore, in 

 some cells the two centrosomes in the prophase were observed 

 while the nucleolus was still present, the difference in size is alone 

 sufficient to prevent confusion ; Voigt has apparently confused 

 them in describing the process of direct division. 



As the eggs mature, they are found on the surface of the ovary 

 and can be readily distinguished by their large size as compared 

 with the surrounding young ova. Associated with the ovary 

 on one side only in most instances, there is found a large mass 

 which is apparently nutritive in character (Fig. 3). An attempt 

 was made to detect the beginning of this modification. The 

 membrane which surrounds the ovary is continuous and passes 

 around the nutritive mass. This structure extends from the ex- 

 treme dorsal part of the ccelome of the seventh somite to the 



FIG. i. A photograph of Branchiobdella instululin contracted. 



ventral body wall (Fig. 3). Several sections show this mass even 

 passing beneath the intestine. Frequently the neural sheath of 

 peritoneum can be shown to be continuous with the sac enclosing 

 this mass and the eggs. All of the masses studied had a faint 

 nucleus and in one instance a nucleolus was found which would 



