276 Miscellaneous. 



plete, thanks to the researches of O. F. Mliller, Valentin, Perrier, 

 A. Agassiz, Wyville Thomson, and several other naturalists, the 

 information furnished by authors as to the histology of the soft 

 parts of these organs is not equally exact. In the hope of giving 

 more precision to the ideas on this subject, we have studied in 

 detail the pedieellariae of the large Urchin, Echinus sjjhcera, Forbes ; 

 and we will describe in a few words the principal results of the 

 investigation. 



On the ophiocephalous pedicellaria of Valentin the three adductor 

 muscles, arranged in the form of a triangle, are attached, as is well 

 known, to the calcareous apophyses of the three valves ; but the 

 fibres which unite the head of the pedicellaria to the club of the 

 stem are not inserted upon calcareous parts, but terminate in an 

 extremely remarkable fashion. Most of them are bent siiddenly 

 upon themselves before arriving at the level of the calcareous parts, 

 and thus form a series of loops or meshes. 



Two bundles only are prolonged further, interlace with the semi- 

 circular arcs of the valves, and terminate freely in a small tuft of 

 meshes in the middle of the muscular triangle. 



Quite distinct and separate from these bent fibres, alternating 

 with them, and external to the calcareous parts, we find three parts 

 of a still more curious structure. These are a sort of grilles or 

 gratings, formed of fibres repeatedly bent, composing a series of 

 meshes. These organs are not attacked by dilute acetic acid ; they 

 have the aspect of elastic tissue ; and it seems probable that they 

 function as antagonists of the adductor muscles, and serve to open 

 the valves, somewhat like the ligament of an acephalous moUusk. 



The tridactyle and gemmiform pedieellariae contain these grilles ; 

 but they are very difficult to find, in consequence of their extreme 

 delicacy. The fibres of the stem are not bent upon themselves, but 

 attach themselves directly to the calcareous parts. 



The head of the gemmiform pedicellaria is an extremely compli- 

 cated organ. There is a gland outside of each valve ; it is covered 

 with two layers of muscular fibres and with a cylinder epithelium. 

 These pedicellarise are perhaps organs of urtication, for their calca- 

 reous valves terminate in a needle-point ; or they may be organs 

 for the secretion of mucus, as Mr. 81aden thinks, who has recently 

 described the histology of this kind of pedicellaria in ^ph(xrechiniis 

 granaJaris (Lam.)*. 



At the commencement of histological researches the observations 

 upon the structure of the muscles of the Echinodermata were 

 always comj)letely contradictory. Wagner, Siebold, and Johannes 

 Miiller described these muscles as being unstriped ; Valentin, on 

 the contrary, maintained that the muscles of the lantern and of the 

 spines of the Urchin are striped ; and De Quatrefages saw a stria- 

 tion upon the longitudinal muscles of Synapta. Baur contradicted 

 these observations, whilst Leydig described a longitudinal and 

 transverse striation in Echinus and Holothuria. Finally, in the last 



* Ann. & Mag. Nat. Hist., August 1880. ■ 



