464 MONTGOMER Y. [Vol. XV. 



this substance would superinduce the lilac staining of the 

 chromatin threads. This addition of a probably nutritive 

 substance would seem necessary, in order that the amount of 

 the chromatin continue to increase as the nucleus itself grows 

 larger. Subsequently all that nutritive substance attached to 

 the chromatin threads would seem to become metamorphosed 

 into chromatin, since in the largest germinal vesicles these 

 threads again stain a deep blue. And as a matter of fact, the 

 quantity of the chromatin must increase with the growth of the 

 ovum, since it can easily be demonstrated that in the larger 

 nuclei there is an absolutely greater amount of this chromatin 

 present than in the nuclei of the primitive peritoneal cells.' 



II. Piscicola rapax (Verr.) (= Pontobdella rapax Verr., which 

 Dr. Percy J. Moore assures me is a true Piscicola). 



(Plate 29, Figs. 300-316.) 



(The ovary is a tubular, contorted sack ; from its inner sur- 

 face numerous smaller, likewise tubular (round on cross-section), 

 acini project into its cavity, each acinus containing numerous 

 ovogenetic stages, the least mature of which lie at its pro.ximal 

 end, the most mature at its distal. These several acini are 

 not continued as far as the external opening of the ovary, but 

 their distal ends apparently open into a large ovarial cavity, 

 and the ova drop into this cavity before they can arrive at the 

 external genital opening. Each single acinus of this leech may 

 be compared to either of the two whole ovaries of Ascaris) 



The youngest ovarial stages are small ovogonia in stages of 

 mitotic division (Fig. 300). In them no nucleoli were to be 

 seen ; a minute nucleolus might be present in each of these 

 nuclei and be obscured by the dense mass of chromatin. In 

 all stages subsequent to these a single nucleolus is present in 

 the nucleus (now a germinal vesicle) until the pole spindle is 

 formed ; in the smaller nuclei the nucleolus is usually oval, in 

 the larger ones spherical. The growth of the nucleolus keeps 



^ For the researches of other authors on germinal spots of polychaetous anne- 

 lids, cf. the reviews of the papers of Korschelt ('89, '95), Graff ('88), Giard ('81), 

 Vejdovsky ("82), Eisig ('87), Fraipont ('87), Mead ('95), Fauvel ('97), Michel 

 ('96), and Carnoy ('84). 



