638 TRANSACTIONS OF SECTION D. 



series. Here I may add, however, that in a few birds obtained towards the end 

 of April the testes were as large as those of the other Sanderlings obtained 

 a month later, and were probably rapidly on the road to functional activity. 

 But the flocks from which these birds were obtained only tarried a few days 

 on the coast, and I believe that the birds were mature not only from their plumage 

 and behaviour, but also owing to the comparatively large size of the seminiferous 

 tubules, though while spermatogenesis seemed to be commencing, fully formed 

 and ripe sperm-cells (spermatozoa) were not present. Histologically the condition 

 of such testes resembled that maintained in the glands of a mature Hedge- Sparrow 

 procured in late February. Should one have been able to examine the testes of 

 these Sanderlings in the beginning of June they probably would have been 

 1'2 cm. in greatest measurements and quite functional. In subjecting thin sections 

 to microscopical examination, a striking difference could be made out between 

 those of Calidris arenaria and of many shore-birds in which the glands were 

 actively functional. Apart from the countless swarms of spermatozoa which 

 occupied the seminiferous tubules in the latter, the tubules themselves were 

 markedly larger. The proportion between the two is at once manifest when with 

 a ^-in. objective and No. 2 Huygenian eye-piece fitted to the usual 10-in. microscope 

 tube one finds in the active glands a single tubule, in contrast to some forty to 

 sixty tubules of the inactive glands occupying the whole field of the microscope. 

 The testes of the Sanderlings were all embedded in paraffin, cut in ribbons, and 

 mounted as serial sections. The time taken in examining complete series has been 

 considerable. I feel, however, safe in stating that, apart from the phenomenon of 

 semination in the testes of the birds obtained toward the end of April, while 

 a certain amount of spermatogenesis has taken place, this has passed throueh 

 more or less abortive phases, no real functional activity having been reached. 

 Yet I would not like to insist that no Sanderlings in pre-nuptial plumage breed. 

 The species no doubt varies individually within limits (as in the case with other 

 animals) in arriving at maturity, some birds being more precocious than others. 

 However, with regard to Sanderlings which occur along our shores during the 

 period when they ought to be nesting, those birds not pairing seem to split into 

 small parties and to lead a sort of nomadic life from shore to shore, being some- 

 what inconspicuous even to the trained observer until about August when they tend 

 to muster; while in September they join company with migrants coming from 

 northern climes, the latter, as a rule, being young "birds in first autumn plumage. 

 Thus are formed flocks of young and partially matured birds, hitherto spoken 

 of as adults and young. The fully adult birds apparently arrive later (about 

 October). I do not consider them at all as plentiful along our coastlands. 

 Probably many pass on to southern climes before mid-winter. 



Before concluding I may say that there is reason to believe that other species 

 of shore-birds take more than one year to reach maturity, and that prior to this 

 period their desultory migratory movements correspond in the main to those 

 of the Sanderling. Here, then, investigations into the question of semination 

 afford a key in the elucidation of some points of importance dealing with avian 

 migration and geographical distribution. 



WEDNESDAY, SEPTEMBER 7. 



The following Papers were read : — 



1. The Anatomy and Physiology of Calma glaucoides. 

 By T. J. Evans. 



2. Some Anatomical Adaptations to the Aquatic Life in Seals. 

 By H. W. Marett Tims, M.A., M.D. 



Certain anatomical adaptations to life in the water are to be found in all 

 purely aquatic animals, e.g., expansion of the posterior end of the body, modifica- 

 tion of the limbs, shortening and practical obliteration of the neck region (as 

 far as external appearance) and modifications of the larynx. 



The details of these structural adaptations in the seal have been fully 



