258 FRESH- WATER EHIZOFODS OF NORTH AMERICA. 



gradually assumed an oval and then an irregularly five-sided shape, as 

 represented in fig. 8, pi. XLV. Continuing its slow changes, it elongated 

 to more than double its former extent, becoming narrower and constricted 

 toward the middle, as seen in fig. 7. In the latter condition, the group was 

 more spread, thinner, paler, and more translucent, and the individuals 

 more widely separated. Later the group rather suddenly shortened to an 

 oval shape, then became irregularly quadrate, reniform, and so on 



Another group, when first noticed, was biscuit-shaped, and as it slowly 

 moved along, a break occurred near the centre, through which, by a slight 

 change of focus, a deeper layer of individuals could be seen, apparently 

 indicating the group to have formed a hollow mass. 



The individuals composing the groups of Diplophrys have appeared to 

 me to be associated by means of a transparent protoplasm ; but the exist- 

 ence of this has been denied by Hertwig and Lesser, in opposition to 

 similar views expressed by Archer, Greeff, and Schulze. 



Hertwig and Lesser describe the larger groups or communities as 

 being made up of smaller ones associated in fours; but such did not appear 

 to be the case in the few examples which came under my observation. 



The individuals composing the groups were of pretty uniform size, 

 globular in shape, and measured 0.004 mm. to 0.005 mm. in diameter; 

 therefore considerably smaller than those described by Hertwig and Lesser. 

 They were transparent, and contained mostly a single, bright cherry-red 

 corpuscle, oil-like and highly refractive. The presence of the large red 

 corpuscles so far concealed everything else that I failed to detect a nucleus. 



The pseudopodal rays were numerous, and diverged irregularly from 

 all parts of the surface of the groups. They were exceedingly delicate, 

 straight, simple, non-granular, and from 0.02 mm to 0.04 mm. long. I 

 could not trace a connection between them and the individuals, aud sus- 

 pected that they emanated from a common enveloping protoplasm, accord- 

 ing to a similar view of Professor Schulze. 



ACTINOSPHiEPJUH. 



Greek, akiin, a ray; sphaira, a sphere. 



Body spherical or oval, composed of finely granular protoplasm en- 

 closing a mass of delicate polyhedral vesicles or vacuoles occupied by a 

 clearer hyaline protoplasm. The outer one or two layers of vacuoles more 



