TRANSACTIONS OF SECTION D. 735 



Liverpool Bay, tliougli from its general resemblance to Dias longiremis he considers 

 it probable that it may have been previously overlooked, the points of difference, 

 though important, being only distinguished by careful microscopical examination. 

 Pontella l\'oUasto7ii , first described by Sir Jolm Lubbock in 1857, from 

 specimens taken by him at Weymouth, has not since been recorded as occurrino- 

 iu British waters until now found in Liverpool Baj\ This and the previously 

 named Copepoda were illustrated by drawings taken from specimens freshly- 

 preserved. 



In conclusion the author stated : The presence and distribution of Copepoda 

 in our seas are most vitally interesting, forming as they unquestionably do by far 

 the largest proportion of the life of the ocean. And being themselves of the utmost 

 purifying utility as refuse-gatherers, they transform the same by their internal 

 biological and chemical laboratories into food for higher orders of pelagic denizens, 

 these again furnishing in illimitable quantity the food of man. 



8. Marine Zoology in Banka Strait, North Celeles. 

 By Sidney J. Hickson, M.A. 



9. Proposed Co7itributions to the Theory of Variation. 

 By Patktck Geddes. 



With reference to a forthcoming more extended discussion of the laws of varia- 

 tion (in the article Variation and Selection of the ' Encyclopedia Britannica ' 

 and elsewhere) the writer desires to submit for discussion (1) an hypothesis of the 

 internal mechanism of variation in terms of the familiar antagonism between vege- 

 tation and reproduction, this being treated especially in its bearing on the physio- 

 logy, morphology, and natural classification of plants ; (2) a Irindred hypothesis, 

 but treated with special reference to the animal kingdom, which endeavours to 

 account (1) for the variations in bulk (2), for at least many cases of the extinction 

 of species. 



10. On the Early Stages in the Development o/-' Antedon Rcsacea. 

 By H. Bury, B.A., F.L.S. 



Segmentation is regular. The mesoderm is not formed until after the invagina- 

 tion of the archenteron, and arises solely from the latter and its derivatives. 

 Immediately after the closure of the blastopore the archenteron splits into two 

 halves: (1) anterior, becomes constricted in the middle and soon divides completely 

 into the right and left body-cavities ; (2) posterior, gives rise to three cavities-1 

 (n) the gut which forms a ring round the constricted part of the peritoneal vesicle ; 

 (l>) the hydrocele on the right-hand side ; (c) an unpaired posterior body-cavitv. 



The 'yellow cells' appear before the larva is free. 



The free larva has five ciliated bands, the posterior one being incomplete ven- 

 trally. The right and left body-cavities are now anterior and posterior respectivelv : 

 the left body-cavitv forms five longitudinal chambers in the stem ; tlie hydrocele 

 forms an incomplete ring on the ventral side of the gut : and the unpaired bodv- 

 cavity opens to the exterior by a pore (water-pore) on the right-hand side. 



The larva now fixes itself by the ' pseudoproct.' The ' jjseudostome ' invaginates 

 and becomes rotated round to the a.nterior end, where it forms the tentacular cavitv. 

 The right and left body-cavities grow round to the ventral surface, and there form 

 two L >ngitudinal mesenteries; in the anterior of these the stone canal depends 

 from the water-vascular ring, and ojiens into the unpaired body-cavity, which is 

 now quite small. 



The anus subsequently opens (with rare exceptions) in the same interradius as 

 the stone canal. 



Skplefon. — At the top of the stem three underbasals are formed, the smallest of 

 which is situated iu the left dorsal radius, i.e., just opposite the anal interradius. 



