196 



HARD WICKE ' S S CIE NCE - G SSIP. 



in almost every sheet of water or pond that supports 

 rotiferan life of any kind. More especially I find 

 them in shady wells, which here are built in the 

 walls of many of our lanes, leading to the various 

 farms on the hill-sides. Although common, I have 

 never been fortunate enough to procure them in large 

 numbers, as they are rather solitary in their habits, 

 so that it is, generally speaking, somewhat of an 

 accident when I come across them. In my aquaria 

 I can generally find them on the sides nearest the 

 light, foraging among the threads of confervse and 

 oscillatorise, which cover the glass like a close felt. 

 It would seem however that, although by no means 

 a rare rotiferan, it is only partially distributed, as 

 Dr. Hudson informed me some two years ago that he 

 had never seen a rotifer of this genus. The characters 

 of the genus as given in Pritchard are as follows : 

 " They have two frontal eyes, a furcate foot, and a 

 compressed or cylindrical lorica. The lorica is said to 

 be open upon the under-side ; a compound rotary organ 

 is present in all, over which projects a retractile frontal 

 hook ; an cesophagal bulb with two jaws, in two species 

 with two or three teeth ; the oesophagus very short ; 

 two species have a constricted stomach, the others 

 have a simple alimentary canal, all with glands. 

 The two red frontal eyes are delicate ; in C. uncinates 

 and C. bicuspidatus they have escaped observation ; 

 all have peculiar vesicles at the back," subsequently 

 said to be arranged in a circle. 



A few notes upon some of these characters may be 

 of interest, and I will take them in the order given. 

 Owing to the dorsal arch of the lorica, it is, I believe, 

 impossible to see the eyes on that aspect, and only 

 one is visible on a side aspect, as, being situated 

 rather low down, it is impossible to have them both 

 in focus at once ; but in the species in which eyes are 

 visible they are no more "delicate" than in any 

 other rotifer of a similarly small size. In my C. 

 uncinatus I have not been able to detect them ; but it 

 is possible that a strong reflected light might render 

 them visible, as in some other rotifers in which these 

 •organs are deep-seated. The grand distinguishing 

 feature, however, is the ventrally open lorica ; and if 

 the student can get a glimpse of that aspect the 

 rotiferan's identity is at once settled, but unfortunately 

 this is, as previously stated, a matter of great difficulty 

 in this genus, and calls forth all one's skill and pa- 

 tience, which are unfortunately not always rewarded. 

 I give figures of the three aspects of Colurus uncinatus, 

 to illustrate these various points. With reference to 

 the " rotary organ " being " compound," I may say 

 that in many of the genera, both of this family and 

 that of Hydatincea it is often difficult to determine the 

 real character of the ciliary wreath (and also of the 

 jaws) ; so much so that Dr. Hudson does not rely on 

 them at all, but trusts to' the "well-marked differences 

 in shape and structure " of the lorica. The rotifers of 

 this genus may, and probably do, have "two jaws" 

 (mallei), but whether there are " two or three teeth " 



would, I imagine, be difficult to demonstrate. The 

 "frontal hook" is now more correctly described 

 as being "a retractile, arched, chitinous plate," but 

 to the tyro its optical appearance presents many 

 difficulties of interpretation. My experience as to the 

 " vesicles " is that the circular arrangement, where 

 it exists, is simply an accidental one, and that these 

 bright yellow oil-globules, which stud the walls of 

 the stomach, are not more numerous in this than in 

 many other genera. I now give descriptions of 

 species figured. 



Fig. 119 represents the various aspects of a rotifer 

 which I believe to be Colurus uncinatus. Characters : 

 lorica (dorsal aspect) compressed, oval, anteriorly 

 pointed, posteriorly somewhat truncated both on 

 dorsal and side aspect ; open on the ventral side, 

 as in Fig. 119 d, with retractile frontal hood; foot 

 three-jointed, toes furcate, about as long as the foot ; 



Fig 



119. — 



Colurus uncinatus. 



eyes (if any) not detected ; mastax small, details not 

 clearly made out. Fig. 119 a, dorsal view, showing 

 how the opening of the lorica reaches right up above 

 the hood anteriorly, and the foot posteriorly ; b, side 

 view, animal swimming ; c, side view, cilia retracted, 

 and showing muscles by which the retraction is made ; 

 d, ventral view of lorica, showing the form of the 

 opening. This is the commonest of the four species 

 of this genus which I have found in this locality. 

 Fig. 120. — In spite of some slight differences with pre- 

 viously published descriptions Dr. Hudson believes 

 this to be Colurus deflexus. Lorica cylindrical, open 

 on the ventral side, and with faint indications of a 

 ridge on the anterior dorsal, which part is also 

 pointed; posteriorly there are two well-developed 

 spines (two-horned) ; tail-foot forked, toes about as 

 long as foot ; eyes, two. Fig. 121. — This differs from 

 the last only in the posterior horns of the lorica being 

 less pronounced, and in the toes being somewhat 

 longer than the foot. Fig. 122. — In this species, on 

 the dorsal aspect, the lorica is truncated posteriorly, 

 in such a way that the lateral joints can hardly be 

 said to partake of the character of horns ; the toes, 

 as in the last species, are rather longer than the foot, 

 and the whole animal is broader in proportion to its 

 length. In this specimen, as in the specimens of 

 C. uncinatus, I have been unable to detect the eyes. I 



