466 Miscellaneous. 



of Argiop6 attached to Fuci, though more commonly attached to 

 stones." 



It therefore appears that the habitat I gave for Kraussia rubra is 

 not quite peculiar to that species, though it certainly is the usual 

 habitat of Kraussia, while in other lamp-shells attachment to sea- 

 weeds is the exception. 



On the Connexion which exists between the Nervous System and the 

 Muscular System in the Helices. By M. Sicahd. 



In his celebrated memoir on the slug and the snail, Cuvier has 

 described the submission (to use the term which he has employed) of 

 the nervous to the muscular system. It is established, in his opinion, 

 by the close cellulosity which unites the retractor muscles of the great 

 tentacles to the envelope of the cerebroid ganglia, and the principal 

 lobes of the retractor muscles of the foot to that of the suboesophageal 

 ganglia. Since then, every one abides by that assertion ; neverthe- 

 less the union of the two systems is much more intimate than was 

 indicated by Cuvier, and histological study shows that they are 

 directly united with each other. It is not, in fact, simply cellular 

 tissue which joins the nervous centres to the neighbouring muscles ; 

 microscopical examination discloses, in this tissue, the presence of 

 smooth muscular fibres ; so that the nervous system is surrounded by 

 an actual expansion of the muscular apparatus. 



In certain species the arrangement is very manifest, particularly 

 in Zonites algirus — that old Helix of which a great many malacolo- 

 gists justly make a distinct genus. In it clearly marked membranous 

 muscles surround the oesophageal collar. From the upper surface of 

 the retractor muscle of the foot, from the outside, and for nearly 

 half its length, there starts on each side a Httle muscular band two 

 millimetres in width, which soon divides into two lobes, the outer 

 of which, the external, goes to the superior, and the other to the 

 small tentacle ; these muscles are known as the retractor muscles of 

 the tentacles. Now the little band which constitutes the second of 

 these muscles enlarges, spreads like a fan on the internal side to 

 unite with the neurilemma of the oesophageal collar, and thus form 

 with its fellow a sort of muscular framing ; then this muscle goes 

 to the little tentacle with the nerve which is destined for it. On the 

 other hand the muscular bundle which goes to the superior tentacle 

 receives into its interior the tentacular nerve, which, from its point 

 of origin on the suboesophageal ganglion to the point where it enters 

 into the cavity of the retractor muscle, is accompanied by a muscular 

 band, which envelops it and which thus unites the nervous centres to 

 this muscle. 



The connexion just described, of the retractor muscles of the ten- 

 tacles with the oesophageal collar, and the union of these two 

 muscles behind into a single primitive bundle, would make it more 

 proper to designate this muscular whole the common retractor 

 muscle of the tentacles and nervous collar. The action, however, is 

 not so simple as this denomination would seem to indicate ; for if 



