100 ANATOMY OF THE ANOPLA. 



A similar omission is made by Huschke, in describing his Nbtospermus drepanensis, which he pro- 

 vided with an external longitudinal and an internal circular layer. H. Rathke gives Borlasia 

 striata two coats — an epidermis and a corium — combining under the latter both the pale and the 

 pigmentary portions of the skin. He has not noticed the external longitudinal muscular 

 layer, and mentions only an outer circular and an inner longitudinal muscular coat. It is some- 

 what difficult to comprehend the views held by M. de Quatrefages with regard to the same struc- 

 tures, since his descriptions and figures do not seem to coincide with each other. He divides the 

 skin into three coats, viz. the ciliated epidermis, cutis, and the fibrous coat. Moreover, the 

 cutis has two layers — an outer, formed of a homogeneous transparent substance, presenting in its 

 mass a number of cells or simple rounded vesicles, refracting the light, and an inner, of lame 

 elongated cells in a double row ; but in his figure the muscular elements occupy a bulk so insig- 

 nificant that some error appears to have been committed, especially as the third layer of the skin 

 is stated to be a transverse fibrous one. It is at all events difficult to see how the enlarged trans- 

 verse section in pi. 23, fig. i, agrees with his figures iv and v, pi. 18, of the ' Voyage en SicihV 

 Two muscular coats only are described by this author — an external longitudinal and an internal 

 circular — the internal longitudinal being omitted, or rather considered an aponeurotic layer. 

 He also commits a serious error in affirming that the structure of the dermal tissues in the 

 Enopla corresponds with that in Borlasia anglice. Frey and Leuckart likewise describe only two 

 muscular coats — an outer longitudinal and an inner circular. Prof. Keferstein, while repre- 

 senting the cutaneous textures of Cerebratulus (one of the Anopla) with greater accuracy, also falls 

 into the mistake of applying what he found in this animal to all the Nemerteans. He describes 

 two coats in the skin — a cuticula covered with cilia, and an inner thick, finely granular 

 layer which contains the pigment — a definition which is scarcely comprehensive enough for the 

 nature of the parts in such as Lineus marinus. He mentions the occurrence of crystals of the 

 form of arragonite in the pigmentary layer of Cephalothriw ocellata, but such have not been seen 

 in the British forms, except under the action of chemicals, or after the evaporation of the salt 

 water. He also refers to a " transverse" tactile papilla on the snout of his Ceplialothrix longissima, 

 which resembles a slight protrusion of the lining membrane of the canal for the proboscis. 

 His statement, that in Cerebratulus marginatus there are four muscular coats — an external circular 

 under the pigment-layer of the cutis, a longitudinal, a circular, and lastly an internal longitudinal 

 — has already been noticed. No more than three muscular coats are present in the Lineidce. 

 Lastly, Dr. Anton Schneider, 1 in his remarks on the muscles of worms, and their importance in 

 the system, states that in Nemertes the following layers occur : — Circular, longitudinal, and 

 circular, besides radiating muscles — a description that is unsatisfactory as regards the British 

 species. 



The elaborate system of muscles in the body-wall of these worms enables them to perform 

 the most varied and complex motions, so that they have not inaptly been compared to a piece of 

 living caoutchouc. When irritated, the larger species, such as Lineus lacteus, Mont., and 

 Z. sanguineus, suddenly contract in a spiral manner like a cork-screw or the stalk of a Vorticella, 

 or twist their bodies into a rope of various strands. The great Lineus marinus may now and then 

 be observed in its native pools extended between the Fuci of opposite sides in numerous loops, 

 each several yards in length, and so intricately arranged that they can scarcely be unravelled 



1 e 



Archiv fur Anat./ 1864, p. 595. 



