NOTOMMATAD^E. 25 



sensibly at three-fourths from the head, and thence, more or less abruptly, diminish- 

 ing. It is rather deeper (viewed laterally, fig. 2a), the dorsal outline rising to about 

 the middle, thence falling to the tail. The ventral line is nearly straight, only that the 

 ciliated face, almost quite prone, extends fully one-third of the length, and there forms 

 a sort of projecting chin. The outline of this part is, however, very flexible and 

 versatile. The dorsum terminates in a minute conical tubercle, beneath which the 

 cloaca opens ; so that it is a true tail. Below this is a very short and inconspicuous foot, 

 and two minute furcate conical toes. The front is rounded, and can evolve two small 

 hemispherical auricles, very observable, because they are freely protruded, even when 

 the animal is not swimming, but pushing its way among the tangled algae. The mastax 

 is ample, and the trophi of the normal pattern ; behind, the brain descends low into the 

 occiput, and carries a dark red eye near the middle of the sac. I have not seen this 

 sac so pyriform as Prof. Ehrenberg has figured it. It is, in general, turbid toward the 

 lower part, and sometimes quite opaque with angular chalk-masses. A large stomach 

 and intestine, with gastric glands ; a wide ovary ; indications of a vascular or branchial 

 system, and a small contractile vesicle, are all normal, and require no remark. The 

 animal is usually tinged with an olive-brown hue, especially in the abdominal viscera. 



Both the form and manners of this species strike the observer, at once, as unusual. 

 It swims almost constantly ; and affects the surface when in freedom. It makes a 

 smooth rapid course, devious, and apparently objectless ; probably, however, governed 

 by aims which we cannot appreciate. For it frequently makes little darts and jumps 

 as it goes, with a sensible snap of the jaws, as if it took invisible prey. A number of 

 examples occurred in water collected by Mr. Bolton from a ditch in Button Park, 

 Birmingham, and specially marked " surface." 



I presume this to be the N. saccigera of Ehrenberg, from the general form, the long 

 pointed head, the long prone ciliated face, the short toes and shorter foot. Yet he has 

 not noticed the auricles, nor the opacity of the brain. The former, however, are re- 

 tractile ; and the latter varies much. P.H.G.] 



Length, ^^ to -j^-g- inch. Habitat. Birmingham (P.H.G.). 



N. NAIAS, Ehrenberg. 



(PI. XVIII. fig. 2.) 

 Notommata najas .... Ehrenberg, Die In/us, p. 429, Taf. lii. fig. 2. 



[SP. CH. Of large size, fusiform; brain clear; head broad, obscurely auricled ; 

 foot long ; toes short, pointed. 



This is a large and imposing form, evidently approaching the genus C opens, yet 

 showing no visible sense-organs projecting from the trunk. Its claim to a place in the 

 present genus is slight, for the brain has no opacity, there is no tail, and the auricles, 

 if present, are small, and appear to be permanent, as globose ciliated knobs, not evertile. 

 Yet there is no prone face, and the general appearance and structure show affinity with 

 these higher forms. The body is nearly cylindric, somewhat ventricose ; the head nearly 

 of the same width, divided into several broad but shallow lobes, the cilia on which make 

 independent whorls. The mastax is ample, the jaws of the normal pattern. A brain 

 descending into the occiput, and carrying a transversely ovate dark-red eye near its 

 middle, 1 is flanked by a shorter sac on each side ; another point of resemblance to 

 Copcus. A small antenna projects from the occiput. Several annular folds of the skin 

 false joints encircle the body, three in the anterior half, and one distinguishing the 

 trunk from the foot. The latter consists of three well-marked joints rapidly diminishing, 

 terminated by two forked acute toes which are rather short. Two pyriform mucus- 

 glands run through the foot from the toes. The branchial system is well displayed : 



1 Eckstein figures two tentacular brushes of setae on the front, with a crimson eye-speck at the 

 base of each. 



