Proceedings of the British Association, 447 



wanting opercula, of which S. tubularia is the type. All the triangular 

 serpulse they met with were Pomatoceros tricuspis. In 12 fathoms, at 

 the entrance of the Menai Straits, they dredged the shell of Helix aspersa, 

 the common snail, covered with barnacles and serpulse, and inhabited 

 by a hermit crab. 



'On the Reproduction of Lost Parts in the Crustacea,' by H. D. S. 

 Goodsir. — That all the species of Crustacea are endowed with the power 

 of regenerating parts of their body which have been accidentally lost, 

 is a fact which has long been known. The manner, however, in which 

 these are developed, and the organ also from which the germ of the 

 future leg is derived, has never yet been either properly explained or 

 examined. If one or more of the distal phalanges of the leg of a com- 

 mon crab be torn forcibly off, the animal instantly throws off the re- 

 maining parts of the limb. This is effected with little apparent exer- 

 tion, and always takes place at one spot, which is marked externally by 

 a delicate line, covered with an annulus of thinly scattered hairs. The 

 phalanx on either side of the ring is considerably contracted ; and when 

 the shell is taken carefully off, so as to expose the contents, they are 

 found to consist of a fibrous, gelatinous, glandular-looking mass- -the 

 organ which supplies the germs for future limbs. Some hours after the 

 limb is thrown off, the small foramen becomes gradually filled by a small 

 rounded body — the germ of the future leg — which gradually increases 

 in size, so as to push out before it the cicatrix which had been formed 

 on the raw surface after the injury, and now forms the external cover- 

 ing of the young limb. As the germ increases in size, the inclosing 

 membranes become thinner and thinner, until they burst, when the 

 young limb, which has hitherto been bent upon itself, becomes extend- 

 ed and has all the appearance of a perfect limb, except in size. 



1 On the Fishes of Yorkshire,' by T. Meynell. — The total number of 

 species which have been detected as inhabiting the shores or frequent- 

 ing the fresh waters of Great Britain, are stated by Mr. Yarrell's sup- 

 plement to be about 250, of which number Mr. Meynell presented a 

 list of 140 species as frequenting the waters of Yorkshire. 



Dr. Carpenter then communicated to the Section some observations 

 on the position which he deemed ought to be given to the compound 

 ascidians in the zoological scale. In opposition to Milne Edwards, he 

 considered that the compound ascidians should be placed with the 

 Mollusca, and the ascidian polyps with the Radiata. 



Prof. Allman did not think the polyps should be classed with the 

 Radiata. They were not zoophytes — they were not mollusca.— Prof. 

 E. Forbes agreed with Dr. Allman, that we were not in a position to 

 change the place of compound ascidians in the zoological scale. 



3 M 



