84 • JOURNAL OF THE 



ingly a small piece- of the substance was spread out on a 

 slide and examined, when, to my surprise, it was found to 

 be composed of snn-animalculse of various sizes, among 

 which were other bodies, the true nature of which I did not 

 at first quite understand, but which on close examination 

 proved to be the young of the larger heliazoa. So numer- 

 ous, indeed, were the young heliazoa that not a single field 

 of the one-fifth objective and a ocular could be chosen in 

 which there were less than half a dozen, and usually the 

 number was very much greater. 



Such an unusually great and rare opportunity to study 

 these animals could not be neglected. Fortunately they 

 were discovered in the morning, and by close and constant 

 observation for several hours their true relations to the 

 numerous small bodies were satisfactorily demonstrated and 

 proven to be different stages of the same animal. 



For a description of A. Eichoniii and of its habits see 

 "Fresh-water Rhizopods of North America," by J. Leidy, p. 

 259. Plate XLI. 



We will pass at once to the special subject in hand, 

 beginning, for convenience, with the simplest or youngest 

 heliazoan. 



Development. — Let it not be understood that the order 

 in which I am now to describe the different stages of devel- 

 opment is the order in which I observed them. On the 

 contrary, what I shall first describe really came about last 

 in my observations, since I did not at first take the young- 

 est stages of this heliazoan to have any connection with 

 the larger heliazoa. My observations began with an 

 undoubted heliazoan of this species (Fig 13 of my plate), 

 and from that I worked both ways, but principally to the 

 younger. It would have been impracticable to have 

 watched the development of a single heliazoan from the 

 very youngest individual to the full-grown animal, since it 

 would have required not only a constant observation for a 



