678 



SYSTEMATIC HISTOKY OF THE TNFTJSOHIA. 



constricted and tlirowai into folds or 

 wrinkles by transverse tilamentous 

 muscles, hung like hoops within the 

 integument, to which Cohn believes 

 them attached only by a few interrupted 

 points. These muscles were regarded by 

 Ehrenberg as vessels. The contractile 

 influence of these and similar muscles 

 occup}^ng the lower parts of the body is 

 antagonized, according to Leydig, by the 

 elasticity of the cuticle, but according to 

 Cohn by the pressure of the compressed 

 fluids of the body. Longitudinal con- 

 traction of the body effected by nume- 

 rous muscles proceeding from the head 

 backwards to the centre of both sides of 

 the body and thence to the foot. Ehren- 

 berg counted nine, which number Cohn 

 regards as correct. The latter observed 

 A acuoles and what appeared to be nuclei 

 in the substance of the muscles, but no 

 transverse strise. Two bodies at the base 

 of the toes Ehrenberg regarded as muscles 

 moving those organs ; but Cohn believes 

 them to be glandular, secreting an ad- 

 hesive fluid by which the creatiu'e at- 

 taches itself to other bodies. 



Digestive canal consisting of an oral 

 orifice (xl. 1 a), buccal cavity, pharyn- 

 geal bulb (1 c), oesophagus (1 d), stomach 

 (1 e), intestine terminated by a cloacal 

 orifice at If, and gastric glands. The 

 buccal cavity a short passage from the 

 mouth (la) (located on one side of the 

 head) to the pharjTix (Ic), which is large j 

 and, according to Cohn, a muscular mass 

 invests the jaws, which are complex 

 and not easily interpreted, but consist of 

 several parallel teeth (xxxviii. 34) ar- 

 ranged in two sets and attached to a 

 complicated pp'iform organ: respecting 

 the details of their form, authors differ. 

 A constricted passage (1 d) conducts from 

 the phai-jTix to the stomach (1 e), which 

 is large and oblong ; its walls are saccu- 

 lated, or expanded into numerous lateral 

 pouches or pockets opening into the 

 cavity of the stomach, the whole lined 

 by delicate cilia (xl. 4). A narrow 

 pvlorus separates this organ from a short 

 conical intestine, the narrow extremity 

 of which temiinates at the cloaca (1/ ), 

 opening near the posterior extremity of 

 the body on the opposite side to that on 

 which the mouth is situated ; two large 

 pyriform bodies, supposed to be glan- 

 didar, are suspended by narrow peduncles 

 on each side of the phaniix. 



Connected with the cloaca is a large 

 contractile vesicle (1 (/), from which 

 ascend two water- vascular canals (1 i), 

 convoluted at intervals and giving off 



small twigs which support tremulous 

 tags (xE. 5). Ovarium a large pja-iform 

 sac (1 h), connected with the cloaca by 

 a narrow oviduct ; it consists of a thin 

 membrane distended by a granular fluid, 

 in which are seen numerous genninal 

 spots. A small body, supposed to be a 

 cerebral ganglion (Ik), is situated on 

 one side of the oesophagus, and is con- 

 nected with a small setigerous gi'oove on 

 one side of the neck by what Cohn be- 

 lieves to be nerves. Male : The Mite- 

 rojjlea hydcdina (xxxii. 393 ; xl. 2) of 

 Ehrenberg has been demonstrated by 

 recent researches to be the male of Hy- 

 dcdina senta. Like that of many other 

 species it has no visible digestive canity : 

 in general form it closely resembles the 

 female, but is much smaller. Its repro- 

 ductive organs consist of a retractile 

 penis (xl. 0«), enclosed in a fold of the 

 cuticle (() d), the opening of which cor- 

 responds with that of the cloaca in the 

 female ; the base of the penis is sur- 

 rounded by a gland (6 b), above which 

 is the large oblong testicle containing 

 spermatozoa, by the side of which, at its 

 lower part, are two small vesicles (6 c), 

 connected with the penis, and filled -svith 

 numerous large granules, xl. 3 repre- 

 sents an immature ovum of Hydatina 

 senta, and fig. 7 the detached spenna- 

 tozoa from the male animal. 



In most cases the female fixes itself to 

 a spot by its foot, and lays several eggs 

 upon the same place, one after another, 

 by sudden contractions ; sometimes, 

 when it is going to lay more eggs, it 

 returns to the original spot. In eleven 

 hom\s after the eggs were laid, vibration 

 of the anterior cilia was observed, by 

 Ehrenberg, within them ; and in twenty- 

 four hours the young escaped from the 

 shell. Many of the ova are said to have 

 a double shell, and leave a bright space 

 between the two at one of the extremi- 

 ties; similar ova are found in other Eota- 

 toria, ha\dng different shapes. In these 

 double-shelled ova the young are slowly 

 developed. Ehrenberg names them ^' last- 

 ing eggs, or Avinter eggs." xxxn. 394 

 represents an animal completely imfolded, 

 seen from the ventral siu-face. The an'ows 

 in the alimentary canal indicate a de- 

 cussating or circulating movement of its 

 contents, produced by delicate internal 

 cilia, and must not be mistaken for the 

 motion of Monads. 



H. hrachydactyla. — Cylindrical, trun- 

 cated anteriorly, and suddenly attenu- 

 ated at the base of the foot ; claws short. 

 On Hottonia, &c. 1-144". 



