ON THE MARINE BIOLOGICAL LAI50RAT0RY, PLYMOUTH. 377 



Mr. Chubb, of University College, London — was also prevented eventually 

 from making use of it. 



In spite of these circumstances, which prevented the utilisation of the 

 table to the full extent, researches of a substantia] character have been 

 carried out. Part of Mr. Punnett's work, 'On Two New British Nemer- 

 tines,' which has been published recently,^ and Mr. Aders' researches on 

 Spermatogenesis, on last year's matei'ial, have been submitted and 

 accepted by the faculty of the University of Marburg as a thesis for 

 graduation. Mr. Randies' report is given below. 



The Committee respectfully request re-election ; but in view of a 

 balance of 8^. 5s. remaining unexpended, they apply only for a grant 

 of 10^., in addition to the balance in hand. 



On the Anatomy of Trochus. By W. B. Randles. 



I occupied the British Association table from July 17 until August 17, 

 1901, during which time I was engaged in collecting and preserving 

 material for a research on the anatomy and histology of Trochus. 



Several species of Trochus are to be found either at or in the vicinity 

 of Plymouth, and are representatives of three sub-genera, viz. — 



Trochus (Gibbula) cinerarius. 

 „ „ umbilicatus. 



,, „ tumidus. 



„ (Calliostoma) zizyphinus. 

 „ „ striatus. 



„ „ granulatus. 



„ (Trochocochlea) lineatus. 



An examination of the internal structure of Trochus shows the close 

 relationship which evidently exists between this genus and Pleurotomaria, 

 the anatomy of which has recently been described by Woodward.'^ 



Especially is this noticeable in T. (Calliostoma) zizyphinus, where, 

 save for the presence of only one gill, the internal structure is almost 

 identical with that of Pleurotomaria. The nervous system is, however, 

 more highly differentiated, there being a nearer approach to concentra- 

 tion of nerve cells into ganglionic masses than obtains in Pleurotomaria. 



T have compared the various species of Ti-ochus anatomically with a 

 view to testing the validity of the division into sub-genera. 



Though the number of species obtainable here is not very large, yet I 

 find that, as regards the sub-genera Gibbula and Calliostoma, definite 

 anatomical differences do occur, which justify the separation of these 

 forms into sub-genera. 



Trochus (Trochocochlea) lineatus, liowever, presents no apparent 

 anatomical differences from the various species of Gibbula ; and though 

 the examination of a single species of this sub-genus is scarcely sufficient 

 to enable one to judge of its validity or not, yet a very close relationship 

 evidently exists Isetween Gibbula and Trochocochlea. I hope shortly to 

 publish the results of my investigation on this genus. 



In conclusion I beg to thank the Britisli Association for the use of 

 their table and to express ray indebtedness to Dr. Allen for his many 

 suggestions and ever-ready help. 



' Quart. Journ. M. Science, vol. xli. part 4, pp. 547-5G-t, Two plates. 

 » g.J.M.S,, March 1901, pp. 215-263. 



