ELISHA MITCHELL SCIENTIFIC SOCIETY. 85 



much longer time than I conld spare, but would also have 

 needed some little care. As it was, I could watch a young 

 heliazoan until it had developed a few stages, and had con- 

 siderably lessened the near supply of food, and then I could 

 find another heliazoan of the same stage as the one just 

 discarded, but which was in more favorable circumstances 

 for further growth. As indicated, the number of heliazoa 

 was enormous, and the different stages were represented by 

 the score. Had I suspected these various stages to have 

 been wdiat they were, there would have been no trouble in 

 finding a complete set, for every gradation from the young- 

 est to the adult was present in great quantities. Fortu- 

 nately there were quite a number of worms — Dorylaimus 

 stagnalis — in the water, and their constant wriggling about 

 kept the heliazoa and other animals in perpetual motion, 

 so that they came in contact with one another, where other- 

 wise they would not have done so. 



A far greater number of observations were made than I 

 shall here describe. Enough were chosen, however, to form 

 a complete series, and accurate drawings made of them. I 

 shall, therefore, describe only those observations which I 

 have illustrated, hoping that the series will be full enough 

 for our purpose. 



I think it is safe to say that were this minute mass of 

 protoplasm which constitutes the youngest heliazoan 

 observed by itself for a little while, no one would mistrust, 

 its true nature or relations. Indeed it was only after a 

 long and continued observation, and that under the most 

 favorable circumstances, that I became convinced of its 

 true nature. It is nothing but a minute spherical mass of 

 finel\- granular and hyaline protoplasm, 14.5 21 in diameter, 

 with a contained nucleus and a distinct nucleolus (Fig. i). 

 In appearance it resembles white blood corpuscles with a 

 distinct and sharply defined nucleus. Later, however, a 

 vacuole appears in its substance, and, increasing in size. 



