OF TnE nYDATIN.EA. 



68: 



Laterally there arc two longitudiual dorsal muscles ; the frontal region has 

 little homs, pro\ided with bristles ; and upon the breast are six strong styles, 

 or barbs, forming two clusters, which move in a fin-like manner. The oeso- 

 phageal head has two single- toothed jaws ; oesophagus short ; alimentary 

 canal with a stomach-hke division, produced by a constriction ; supposed 

 pancreatic glands, two. An ovary exists in both species, and in one of them 

 a contractile vesicle ; a large frontal ganghon and a round red eye indicate 

 the system of sensation. 



The preceding genera of this family, together with two peculiar to himself, 

 yjz. Plagiognatlia and Lindia, form, in the system of Dujardin, the family 

 Flosculariens ; but the genus Polyarthra and a few others in this family of 

 Ehrenberg belong to the Brachioniens of that author. 



From the remarks of the French naturalist, it is to be inferred that he 

 regards the distinction between Polyarthra and Triartlira as insufficient. 



PoLYARTHEA pMypterci (xxxviii. 30, 

 also XXXIII. 400-402 & 425). — Ciliary 

 wreath, according to Perty, not as de- 

 scribed by Ehreuberg and JDujardin, but 

 continuous and symmetrical, with two 

 eminences crowded by setse, besides 

 which are several long styliform cilia. 

 Near the posterior end of the body are 

 two fossae ^\\th. unsymmetrically arranged 

 setae extending from them. Alimentary 

 canal consisting of a conical oesophageal 

 bulb, stomach, and intestine. Stomach- 

 cells ciliated ; contractile sac present, 

 but no water- vascular system seen ; lon- 

 gitudinal muscles striated; abdominal 

 fluid yellowish-red ; ovary somewhat bi' 



fat-globules. No winter ova seen. Em- 

 brs'o ^Tith bluish spots. Ova adhering to 

 the exterior of the body ; only one seen 

 at a time (Ley dig). It swinis quickly, 

 and often leaps, like the water-flea : this 

 last motion is produced by the fins or 

 pinnae, the former by the vib'ratile organs. 

 (Figs. 400, 401, & 425 represent the P. 

 Trigla of authors; but Leydig has decided 

 that it is identical with P. platyptera. 

 Fig. 425 the under side while the ani- 

 malcule is swimming, with the pinnae 

 depressed ; fig. 400 a dorsal view while 

 leaping or springing ; and fig. 401 a side 

 view, right.) This creatm-e is infested 

 with Colacium, Amongst Conferv^e. 

 1-140". 



Genus DIGLENA (?). — Eyes two, frontal ; foot forked. Excepting the 

 foot and rotary organ, they have no external prominent organ, though some 

 protrude the teeth in a pincer-like manner. The oesophageal bulb has single- 

 toothed jaws ; the oesophagus is very short, except in D. lacustins ; alimentary 

 canal conical, simple, in six, and constricted in two species. In aU, two 

 glands are present, which in D. lacustris are long cylindrical and two- 

 horned ; in the rest they are spherical. The ovary in D. lacustris is band- 

 hke, in the others globose. Contractile vesicles are observed in four species. 

 No species is viviparous ; none carry their egg hanging to them ; transverse 

 muscular bands are seen in three, and in one a vascular network at the head ; 

 tremulous tags are found in three species, in two of which they appear as if 

 attached to the water- vascular-canal glands. The cerebral ganglion is more 

 especially developed in D. lacustris, but is indicated in aU the species by the 

 coloured eyes. 



' teresting animalcide, yvith. a Lynceus — 

 see Microscopic Cahinetj pi. vii. — in its 



DiGLENA lacustris. — Stout, oval, cry- 

 stalline ; the front straightly truncated ; 

 foot suddenly attenuated, in length one- 

 fom-th of the body ; the toes one-third 

 the length of the foot. The transparency 

 of this animalcule is often a great hin- 

 drance to the discrimination of its internal 

 organs, though they are very large ; the 

 superficial skin is delicatelv sliagreened. 

 (xxxni. 403 a side view, left, of this in- 



stomach ; its cimous internal organiza- 

 tion is clearly depicted. Often found in 

 green-coloured water.) 1-70". 



D. grandis. — Long, slender, and cylin- 

 drical, obliquely truncated anteriorlv ; 

 toes straight, longer than the stout foot. 

 The forked central sacculus, near the 

 head, is remarkable, (xxxiii. 404 an ex- 



