TAYLOR : BIOI.OOV OF THE MOLLUSCA. 273 



During the development of the embryo within the egg, the wonder- 

 ful phenomenon, known-as-the " Rotation of the Embryo," takes 

 place. This rotatory, motion is due to the action of the cilial hairs 

 with which the body of the developing mollusk is clothed, and it is 

 remarkable that this motion almost exactly corresponds with the 

 motion of the earth around the sun, the embryo not only revolving on 

 its own axis, but circling round and round the circumference of the egg, 

 like the earth in its orbit round the sun, and with exactly similar 

 motions. This rotation is continued until the embryo is sufficiently 

 advanced to crawl upon and eat its way through the egg-shell, and 

 has then a whorl and a half of its shell already formed. 



They grow little during the first summer, but in the following spring 

 they eat voraciously and grow rapidly, soon attaining their full growth, 

 when their life cycle is repeated. 



Having now placed before you a short summary of some of the 

 peculiarities of structure and habit of a typical mollusk, I trust it 

 has tended to show those who have not hitherto given the subject 

 much attention that there is a great and almost untrodden field of 

 work in studying the organization and habits of these creatures, whose 

 structure is in so many respects so wonderful, and without whose help 

 stratigraphical geology could not have progressed so greatly. 



In conclusion, I cannot help expressing my regret at the enforced 

 absence of our distinguished President, Rev. Canon Horsle)-, and 

 I hope he may be able to be present and that we may be privileged 

 to welcome an address from his li[)s at our next annual gathering. 



Pisidium lilljeborgi Ciessin in the Isle of Skye. — I came across very fine 

 examples of this species last September in a small lake called Loch na Stairsach, 

 behind Broadford, Isle of Skye, at an elevation of some 750 feet. Mr. B. B. 

 Woodward has very kindly examined and verified the species. It was abundant in 

 sandy gravel where a small stream, connecting with another locli, entered. This 

 is an addition to the fauna of vice-county 104, Ebudes North. — J. R. i.e B. Tomlix 

 {Read before the Society, Nov. 8th, 191 1). 



Association of Ancylus fluviatilis and Velletia lacustris. — In a slow-running 

 stream at Leighton Buzzard, Bucks., I found in August last Velletia lacustris and 

 Aucyhts fluviatilis living together on water-lily leaves. The specimens of J^elletia 

 were numerous and small, those oi Ancylus were few but of good size. The un- 

 usual association of the two species seemed to me worth recording, —J. E. Cooper 

 {Redd lefore the Society, Nov! 8th, 191 1). 



