446 EICHARD EVANS. 



account, and came to the conclusion that the granules contained 

 in them were purely vitelline. He must, therefore, have 

 missed that peculiar stage of the development in which there 

 are no small cells in the interior, but only plasmodial aggrega- 

 tions. Maas always found small cells in the interior, either 

 loose or forming flagellated chambers, and hence arrived at 

 the conclusion that the granules, which he supposed to be 

 inside the cells with vesicular nuclei, are all vitelline, thus over- 

 looking the distinction between the yolk bodies, which are 

 really inside the amoeboid cells, and the small nuclei of the 

 flagellated cells plastered to their surface. Another fact helped 

 to establish him in his error, namely, the continual decrease 

 in size of the yolk bodies contained in the amoeboid cells. 



Delage (1), on the other hand, goes to the opposite extreme, 

 for, according to him, the granules in his polynuclear groups 

 are all nuclei of flagellated cells, and are situated inside the 

 cells with vesicular nuclei. He is not in any way impressed 

 by the decrease in size and the complete disappearance of 

 some of the granules in his polynuclear groups, facts which alone 

 drew Maas' attention, and which, as we shall see later on, have 

 influenced Noldeke. The following expression, which occurs on 

 p. i356 of Delage's valuable paper, may throw a certain amount 

 of light on his failure to distinguish between the vitelline con- 

 stituent and the nuclear one in the granules of his " poly- 

 nuclear groups :" — " Chez la larve libre, les cellules amceboides 

 ne contiennent rien autre chose que leur noyau propre.^' I 

 can hardly understand how such an able observer as Prof. 

 Delage made such a statement. But his method of treating 

 the mother sponge and of obtaining the larvae may account 

 for it. He kept the mother sponges in vessels, and instead 

 of providing them with a continuous current he changed 

 their water every twenty-four hours, and thus obtained his 

 larvae only at the time he gave them fresh water. In conse- 

 quence of not providing the sponges with a continuous current 

 they were for nearly twenty-four hours in a contracted condi- 

 tion, and no current passed through them. Therefore no 

 larvae could be hatched, though they might be ready to emerge. 



