1921] NATURAL SCIENCES OF PHILADELPHIA. 153 



Alexieeff, besides, pointed out that Astasia iLagenella) niobilis is 

 very nearly related to de Beauchamp's (2) Astasia captiva, found 

 in a Rhabdocoele, Catenula lemnae, and perhaps might even be the 

 same. 



I have met at different times, in the intestine of several species 

 of Cyclops — prasiniis and others much bigger and which were not 

 identified — an Astasia which easily corresponds to the two forms, 

 7nobilis and captiva, at least in its general characters, but was 

 mostly of a much larger size. Alexieeff, and de Beauchamp both 

 speak of 30-40^^., Rehberg indicates 102-103[j,, but in the form I 

 studied, while the very young individuals which we shall soon speak 

 of were within these limits of size, normal adult or old ones, very 

 likely much enlarged by accumulation of food, reached a much great- 

 er size, some, which in the spherical state generally shown when 

 first isolated from the host, reached as much as 8S\x in diameter, 

 and after a moment, in their full state of elongation, developed to 

 a length of 300[a. 



Let us now examine one of these large individuals (Plate VIII, 



fig. 58) : 



As in all the other species of the group, the organism continually 

 changes in form, its progression being effected by means of swellings 

 and undulations passing from behind forwards. "The metabolic 

 movement," says de Beauchamp, "is perfectly regular; the flow 

 moving from behind forwards, like a large drop which glides along 

 a wire, and there is nearly always a single wave, the posterior end 

 hardly beginning to enlarge by the time the drop reaches the an- 

 terior end." These swellings are sometimes so broad, in compari- 

 son with the narrow interspaces, that the appearance of the animal- 

 cule becomes most singular, like that, for instance, of a tee-totum. 

 The limiting periplast is colorless, thin, but very tough; striated 

 all over with very fine and regular diagonal lines, about 3^[x distant 

 from each other. The body is nearly always entirely filled with 

 grains of paramylum, in the shape of rectangles, but rounded at 

 the ends, 3, 4, and up to 8[jl in length, greenish-opalescent when 

 examined singly; but when seen as a general mass they have a black- 

 ish appearance. These grains represent undoubtedly nutritive re- 

 serves, and diminish in size the longer the animalcule fasts. At 

 the posterior extremity, these grains suddenly turn much smaller. 

 In the plasma are also found a considerable number of tiny, shining 

 granulations, colorless, l[i. in diameter. The nucleus (Plate VIII, 

 figs. 58, 61), lying about in the middle of the body, is spherical, 

 and entirely filled with extremely small granules, which are of 

 variable size according to the individuals. When after compression 

 the very tough nuclear membrane is suddenly rent, there is seen 

 flowing out a large clear area of plasma in which all these tiny gran- 



