408 GENERAL HISTOEY OF THE H^FUSOEIA. 



it as consisting solely of the soft epidermic tissue, or, which is nearly 

 the same thing, of connective tissue. Much discussion has arisen concern- 

 ing the structural composition (i. e., in a word, the histology) of the muscles 

 of Rotatoria. Dujardin and Ecker questioned the existence of actual mus- 

 cular fibres, but recognized a soft contractile substance, often drawn out 

 into threads. The former, however, inchned to the belief in the existence of 

 determinate muscles, although observation, when he wrote, had not made it 

 certain. Thus, at p. 611, when describing a new species of Floscularia, he 

 remarks that, " by gentle compression of the animal, five independent cords 

 were brought into view, contractile and tolerably regular in outline, which 

 perhaps ought to be called muscles ; they extended through the pedicle and 

 to the extremities of the lobes of the rotary organ." 



Ehrenberg noted the presence of muscles in most Rotatoria, and in a few 

 specimens believed he had detected transverse striation, — a fact which would 

 establish an analogy between them and those of the highest animals. This 

 highly-developed organization was denied by Siebold, who described the 

 muscles to be of the non- striated variety so largely distributed among other 

 Invertebrata as well as Yertebrata. But the belief now prevails, that the 

 possession of transversely- striated muscles is one of the characteristics of the 

 Rotatoria, although non- striated fibrils may likewise occur. 



Leydig thus treats this subject : — " The element of muscle is the primitive 

 cylinder, which is of two sorts — fine and thick, — the former in clear homo- 

 geneous threads, which, when traceable, are perceived to be branches of 

 cells ; such occurs piTQcipally in muscular networks ; the latter — the thick 

 primitive cylinder — originates from cells coalesced in rows, and it, therefore, 

 presents internally, at considerable inteiwals, the still- remaining cell-nuclei. 

 These cylinders exhibit a gradual advance in their further histological phases. 

 They may remain homogeneous hke the finest primitive cyhnders, or resolve 

 themselves into a homogeneous sheath, and an axial substance in the form 

 of molecules. Lastly, the contents of the cyhnder may break up into mus- 

 cular (sarcous) particles, and therein approximate to the so-called trans- 

 versely-striped muscles, to which at length it may attain a complete resem- 

 blance." Thus the cell-wall comes to form an investing sheath or sarcolemma 

 of each fibre, and the cell-contents the vital contractile substance, or the sar- 

 cous particles. Leydig adds — '' Both varieties of muscle, simple and striated, 

 occur in the same species, so that the gradual transition of one into the other 

 is unmistakeable." The existence of striated muscle has been noted by Ehren- 

 berg in Euchlcmis triquetra ; by Oscar Schmidt in Pterodina Patina ; by Perty 

 in the foot of Scaridhun longicaudum, in Pohjartlira (XXXYIII. 30 m), in 

 the marginal muscle of Diglena lacustris, and of BracMonus trijjos ; by Leydig 

 in Notommata Sieboldii (XXXYII. 32 a) and Noteus ; by Dahymple, in No- 

 tommata Anglica ; by Williamson and Gosse in Melicerta : and, without doubt, 

 it may be discovered in most other genera (XXXIX. 7). 



Perty has noticed in the foot of Fhsmlaria rows of granules, and fine 

 longitudinal striae, — an intermediate condition referred to in the description 

 of Leydig, given above. Bergmann and Leuckart mention in a note (p. 377) 

 in their work, that in some animals transversely- striated muscles are visible. 

 Prof. Williamson's observations support some of Leydig's views. " ^Tien one 

 of these muscular fasciculi," writes the English naturahst, ^' is drawn out 

 at full stretch, its surface is seen to be marked, at very regular intervals, by 

 dark transverse bars (XXXYII. 18). Each fasciculas has a diameter of about 

 ^J^th of an inch ; and the transverse striae recur at distances of about 

 -g-fjifj-Q-th. These intervals are rather larger than those seen in the fasciculi 

 of human voluntary muscle .... On rupturing the fasciculi transversely, we 



