$$ 29, 30. 
THE POLYPI. 41 
CHAPTER II. 
MUSCULAR SYSTEM AND ORGANS OF LOCOMOTION. 
§ 29. 
The movements of Polyps are performed, 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 strize, although during their contractions there are sometimes, though 
rarely, 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 Eleutheria this muscular system 
is much more apparent. A similar layer, very distinct, is observed in Acti- 
xia, 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 
-striated muscular fibres in Eschara (Ann. d. Sc. 
Nat. VI. 1836, p. 3), must have been deceived. I 
have been unable to perceive them in Eschara, Al- 
-cyonella, Cristatedla, and other species. Nord- 
‘mann also has not found them in Cedlaria. (Ob- 
serv. sur la Faune Pontique, 1840, p. 679; also 
Millers Arch. 1842, p. ccviii.) The irregular bands 
sappearing during contraction, but afterwards disap- 
pearing, have been observed by Quatrefages with 
Edwardsia (Ann. d. Sc. Nat. XVIII. 1842, p. 84, 
pi. II. fig. 7, a-b).* : 
1 Corda, Nov. Act. Acad. C. L. C. Nat. Cur. 
XVITI. 1839, p. 299. Also Ann. d. Sc. Nat. VIII. 
1837, p. 363. 
*[§29, note 1.] Busk has described and figured 
the striated form of this tissue with dAnguinaria 
-patulata and Notamia bursaria. (Trans. Micro- 
scop. Soc. of London, II.) I have been unable, 
however, after considerable search upon many Bry- 
ozoa, among which were several A/cyonella, to 
detect any appearances of this kind ; and I would 
venture a pretty confident eee that in the spe- 
2 Quatrefages, Ann. d..Sc. Nat. XX. 1843, p. 
238, pl. IX. fig. 3-5. 
3 Quatrefages, Ibid. XVIII. 1842, p. 281, pl. 
VILLI. fig. 3. 
4 Bertho/d, Beitr. zur Anat. u. Physiol. 1831, p. 
16 ; also in the body of Edwardsia, Quatrefages 
has found longitudinal and circular fibres (Ann. d. 
Sc. Nat. XVIII. p. 84). 
5 Similar muscles have been observed by Farre 
(Phil. Trans. 1837, p. 387) in Bowerbankia, Vesi- 
cularia, Lagenella and other Bryozoa. Miine 
Edwards has seen them in T'ubulipora and Es- 
chara. (Ann. d. Sc. Nat. VIII. 1837, p. 324; VI. 
1836, p. 23, pl. I. fig. 1,¢,1,d; pl. I. fig. 1, a.) 
Coste has given a very detailed description of the 
cies examined no such form of muscle is present. 
Quite lately, however, the subject has been care- 
fully examined by Aliman (Rep. Brit. Assoc. 1850, 
p. 318), and his descriptions are such as to leave 
no doubt upon the existence of the striated fibre 
with the species he has examined, among which 
are he Paludicellae.— Ep. 
