ENTOZOA. 



127 



Echinorhynchus and other sterelminthoid 

 worms ; but a series of extremely minute close- 

 set parallel transverse lines are brought into 

 view, which are permanent, and depend on 

 the texture of the epidermoid substance itself. 



Although a distinct and general epidermic 

 covering cannot be demonstrated in the more 

 simple Sterelm'mtha, the soft bodies of which 

 entirely dissolve after a few days' maceration, 

 and which, in animals examined soon after 

 death, are often found in consequence to have 

 lost their natural form, and to have degenerated 

 into a kind of mucus,* yet in most species 

 traces of the epidermic system are manifested 

 in some limited parts of the body : thus it ap- 

 pears in the form of hard transparent horny 

 hooklets around the oral proboscis in the Cystic 

 genera, as in the Cysticercus celluloste (Jig. 61), 

 and most of the Cestoid worms. In the Flori- 

 ceps, Cuv., these recurved spines are arranged 

 along the margins of four retractile tentacles, 

 which thus serve to fix the worm to the 

 slippery membranes among which it seeks its 

 subsistence. In the Trematode worms epider- 

 mic spines are seldom developed ; the species 

 which infests the human subject (Distoma 

 hepaticum) presents no trace of them. When 

 they exist in this order, they are either confined 

 to the head, or are at the same time spread over 

 a greater or less proportion of the surface of 

 the body. Of the first disposition we have an 

 example in the Gryporhynchus pusillus, (a tre- 

 matode worm infesting the intestines of the 

 Tench,) which manifests an affinity to the 

 Tten'us armata in its proboscis armed with six- 

 teen strong recurved spines arranged in a 

 double circular series. In the Distoma trigo- 

 nocephalum there are two straight spines on 

 each side of the head. In Distoma armatum 

 the head is entirely surrounded by similar 

 straight spines. In Distoma ferox the head 

 bears a circle of recurved spines. In Distoma 

 denticulatum the head is surrounded by a series 

 of large straight spines, and there is a series 

 of smaller spines around the neck. In Dis- 

 toma spimtlosa the anterior part of the body is 

 beset with reflected spines ; and in the Dis- 

 toma perUttum, Nord., the whole surface of the 

 body is armed with hooklets, arranged in 



Fig. 74. 



Proboscis of Echinorhynchus gigai, magnified. 

 9 Rudolphi, Hist. Entoz. i. p. 230. 



transverse rows, each being supported on a 

 cutaneous prominence and bent backwards, 

 (Mt.fe.91). 



For a description of the complicated horny 

 and cartilaginous parts of the dermo-skeleton, 

 which enter into the mechanism of the suckers 

 of the worms belonging to the genera Diplo- 

 zoon and Octobothrium, we are compelled from 

 want of space to refer the reader to Nordmann's 

 Mikrographische Beitrage, (Erstes Heft.) 



In the Acanthocephala the head, as the name 

 implies, is armed with recurved spines or 

 hooks, which are arranged in quincunx order 

 around a retractile proboscis, (Jig. 74) ; and, 

 in addition to these, some species have smaller 

 and less curved spines dispersed over the neck 

 or body. 



Among the Calelmintha the genus Lingua- 

 tula is remarkable for the development of four 

 large reflected spines, arranged two on each 

 side the central mouth ; and which can be par- 

 tially retracted within depressions of an elon- 

 gated semilunar figure. The worm attaches 

 itself so firmly by means of the horny hooks 

 that it will suffer its head to be torn from its 

 body rather than quit its hold when an attempt 

 is made to remove it while alive. In the 

 Trichocephalus uncinutus the truncated head 

 presents at its anterior margin a series of hard 

 reflected hooks continued directly from the 

 integument. In the Strongylus armatus, which 

 has sometimes a singular nidus in the me- 

 senteric arteries of the Horse and Ass, the 

 globose head is terminated anteriorly by straight 

 spines, but in the Strongylus dent at us with 

 hooklets. Lastly, we may notice the very 

 singular worm found by Rudolphi in the 

 O3sophagus of the Water-hen, and which he calls 

 the Strongylus horridus, where the body presents 

 four longitudinal rows of reflected hooklets. 



The epidermic processes, when thus traced 

 through the different orders of Entozoa, pre- 

 sent but few modifications of form, and 

 have little variety of function ; the straight 

 spines at the mouth serve to irritate and in- 

 crease the secretion of the membrane or cyst 

 with which the worm is in contact; the re- 

 curved hooklets serve as prehensile instru- 

 ments to retain the proboscis and the worm 

 in its position; and when they are spread 

 over the surface of the body, they may have 

 the additional function of aiding in the loco- 

 motion of the species, analogous to the spines 

 which arm the segments of the (Estrus, which 

 passes its larva state, like an Entozoon, in the 

 interior of the stomach and intestines of a 

 higher organized animal. 



Muscular system. Although in every order 

 both of the Parenchymatous and Cavitary 

 worms, living specimens have been observed 

 to exhibit sufficiently conspicuous motions, yet 

 the muscular fibre is not always distinctly eli- 

 minated in them. In the Cysticerci, however, 

 Rudolphi describes two bundles of fibres as 

 arising from the inferior part of the body, and 

 expanding upon the upper pail of the cyst. 

 We have traced corresponding fibres extending 

 to the head in a large Cysticercus tenuicollis; 

 which fibres were doubtless the principal agents 



