•^.'S» 29, 30. THE POLYPI. 41 



CHAPTER II. 



MUSCULAR STSTEM AND ORGANS OF LOCOMOTION. 



§29. 



The movements of Polyps are pei-formed, partly by contractions of 

 the sides of their body, in which are found no muscular fibres, and partly 

 by a true muscular tissue. The fibres of this tissue have not regular trans- 

 verse striae, although during their contractions there are sometimes, though, 

 I'arely, seen irregular transverse bands. ^'^ 



§30. 



In those Polyps having a true muscular system, this tissue is composed 

 of interlaced fibres, forming a layer beneath the skin. A coarse net-work 

 of this kind is seen in the arms of Hydra, although in the foot and rest of 

 the body there is scarce anything comparable to muscular fibres. ^^' Under 

 the skin of Synhydra'-'-^ and in the arms of ELcutheria^''^ this muscular system 

 is much more apparent. A similar layer, very distinct, is observed in Acti- 

 nia, which, in their mantle, is composed of both longitudinal and circular 

 fibres, the contraction of which draws the tentacles together, and this, com- 

 bined with that of the radiating fibres of the foot, gives rise to the various 

 forms of these animals.*^' 



The Bryozoa have the muscular system more apparent; in the cavity of 

 their body completely isolated fasciculi are seen, composed of parallel 

 .fibres, serving especially for the withdrawal of these animals into their cells. 

 These fasciculi arise from the internal surface of the body, and are inserted 

 partly into the base of the tentacles, and partly into the neck and digest- 

 ive canal, — thus serving almost exclusively as retractors of these last.® 



1 Milne Edwards, who declares he has seen 2 Quatrefagc.i, Ann. d. Sc. Nat. XX. 18-13, p. 



striated muscular fibres in Esckara (Ann. d. Sc. 238, pi. IX. fig. 3-5. 



Nat. VI. 1836, p. 3), must have been deceived. I 3 quatre/ages, Ibid. XVIIL 1842, p. 281, pL 



have been unable to perceive them in Esckara, ÄI- VIII. tig- 3. 



cyonella, Cristaiella, and other species. Iford- ■* Bertko/d, Beitr. zur Anat. u. Physiol. 1831, p. 



mann also has not found them in Cellaria. (Ob- 16 ; also in the body of Edwardsia, Quatre/a^es 



serv. sur la Faune Pontique, 1840, p. 679 ; also has found longitudinal and circular fibres (Ann. d. 



Muller's Arch. 1842, p. ccviii.) The irregular bands So. Nat. XVIII. p. 84). 



appearing during contraction, but afterwards disap- 5 Similar muscles have been observed by Farre 



pearing, have been observed by Quatrefases with (Phil. Trans. 1837, p. 387) iu Bowerbankia, Vesi- 



Edwardsia (Ann. d. Sc. Nat. XVIII. 1842, p. 84, cutaria, Lasenella and other Bryozoa. Milne 



pi. II. fig. 7, a-b).* Edwards has seen them in Tubulipora and Es- 



1 Corda, Nov. Act. Acad. C. L. C. Nat. Cur. chara. (Ann. d. Sc. Nat. VIII. 1837, p. 324 ; VI. 



XVIII. 1839, p. 299. Also Ann. d. Sc. Nat. VIII. 1836, p. 23, pi. I. fig. 1, c, 1, d ; pi. II. fig. 1, a.) 



J837, p. 363. Coste has given a very detailed descriptiou of the 



* [ § 29, note 1.] Busk has described and figured cies examined no such form of muscle is present, 



the striated form of this tissue with Anguinaria Quite lately, however, the subject has beep care- 



spatulata and Notamia bursaria. (Trans. Micro- fully e.xamined by Allman (Rep. Brit. Assoc. 1850, 



scop. Soc. of London, II.) I have been unable, p. 318), and his descriptions are such as to leave 



however, after considerable search upon many Bry- no doubt upon the existence of the striated fibre 



ozoa, among which were several Alcyonella, to wilt the species he has examined, among which 



detect any appearances of this kind; and I would are he Paiudirdlae. — Ed. 

 venture a pretty confident opinion that in the spe- 

 4# 



