146 THE AMEKICAN MONTHLY [July, 



Two eyes may sometimes be seen in Rotifei- tardus^ in the neck, 

 just above the mastax, which possibly might cause confusion ; these be- 

 long to a fetal animal ; but one has to look so far down before one 

 comes to the second mastax that it might be a means of easily separat- 

 ing closely allied species. The head is upwards in Rotifer vulgaris 

 and tardus^ downwards in Philodina aculeata^ Philodina tuber ctilata^ 

 and Rotifer macrurus^ but is this invariable? 



The color of this rotifer varies considerably, probably chameleon- 

 like from the tint of the flocculent deposit in which it lives ; some may 

 be found quite a light yellowish-brown ; these are the younger ones ; 

 in these the internal organs are more easily seen ; the. mastax is sur- 

 rounded by a considerable glandular mass, the buccal funnel stands out 

 like a pouch from the front of the animal, its margin fringed with cilia, 

 and leads straight down to the mastax, immediately under which is a 

 large oblong stomach separated by a constriction from a similar shaped 

 but smaller intestine ; on the other side an oval ovai'y fills up the body. 



The antenna (Fig. 3) is long, two-jointed, the joint very faintly 

 marked ; at the end are three small lobes fringed with cilia. The 

 frontal column (Fig. 3) is rather wide in proportion to its length ; 

 among the cilia a small cleft proboscis may be seen immediately before 

 the wheels expand. The tubercules are not well marked, and appear 

 to be formed by the folds of the trunk ; in its fully extended state, when 

 it becomes worm-like, resembling Rotifer vulgaris^ the tubercules 

 almost disappear. 



Philodina aculeata^ frequently found with the one under consider- 

 ation, is of a yellow hue, has the distinctive spines, the wheels do not 

 exceed the width of the body, the spurs are small, and the end joint of 

 the antenna is wedge-shaped, base forward. 



DISTYLA FLEXILIS. 



This rotifer, belonging to the family Cathypnadce^ which includes the 

 common Cathypna luna^ is represented in front view. Fig. 4, and in 

 side view, Fig. 5. Mr. Gosse places it in the genus Distyla with some 

 hesitation; there is indeed but little distinction between Distyla and 

 Cathypna^ the former being longer in proportion to width, and the 

 curious lateral, bellows-like, infolding characteristic of the family being- 

 less marked. 



In this group may be observed something like a state of sleep ; the 

 animal perches on its claw-like toes, bent at an angle under its body, 

 and remains motionless for a time, as if visited by that '' gentle sleep 

 beloved from pole to pole," which most rotifers seem not to require. The 

 little rotifer has to exertise greater perseverance than the little ant to ac- 

 quire its daily provender, and, examine it when you may, from morn 

 to dewy eve, or in the silent watches of the night, it is ever in a state 

 of ceaseless activity. This group is interesting from being an excep- 

 tion to this general rule. 



Distyla Jlexilis is small, about yiQ-inch long and without color, ex- 

 cept the one rose-red oblong eye, and a yellowish tinge in the stomach. 

 The body is covered with folds, giving it an irregular tesselated ap- 

 pearance and making the outline fuzzy under a low power. It is active 

 in its attacks on food, but remains near one spot for a long time, occa- 

 sionally swimming about to seek " fresh fields and pastures new," yet 



