TRANSACTIONS OF SECTION D. 637 



or material (necessarily cytoplasmic since the nuclei are all alike), and polarity. 

 Polarity may be expressed in terms of a graded stratification of materials. In 

 fact, to the adult organism there must be attributed the same organ-forming 

 substances as were present in the germ, and similarly arranged. The difficulty 

 is that the former is divided into differentiated cells. A second difficulty is 

 presented by the anomalous behaviour of the germ-layers, and by the fact that 

 a part in which these substances exist ex hypothesi in other than the correct 

 proportions can yet form a whole. This indicates that the problem is funda- 

 mentally the problem of assimilation, and it should be borne in mind that 

 metabolism and regeneration are just the two functions which depend, in 

 Protozoa, on the presence of the nucleus. 



4. Semination in Calidris arenaria : A Key to some Problems regarding 

 Migratory Movements in the Breeding-Season. By C. J. Patten, 

 M.A., M.D., Sc.D. 



The positive evidence which I now possess of the occurrence of the Sanderling 

 (Calidris arenaria) throughout the summer along various parts of the British coast 

 prompted me to make an examination of the testes with the view of throwing 

 some further light on the question as to the probability of the species breeding 

 in our Isles. From a study of the bird's habits I have already made out several 

 facts which support the view that birds apparently in nuptial plumage, and 

 occurring along the coastlands in our Isles in the height of the breeding-season 

 are not fully matured, and even in their plumage a slight but important difference 

 from the true nuptial garb could be made out. This plumage I have called 

 pre-nuptial, 1 and it is with special reference to birds in such garb that I now put 

 forward the results of my investigations into the condition of the testes at the 

 time when, if active, they should be at the zenith of development. 



I shall have but little reference to make regarding birds in true nuptial 

 plumage, seeing that they do not tarry during the vernal migration along our 

 shores more than a few days, and their occurrence with and departure from us 

 always well precedes the time of the commencement of nesting. 



The remarkable fact that in birds the testes reach a relatively enormous size 

 during the limited period in which they are functionally active is a point which 

 I have kept carefully in view. I have investigated the state of the testes in a 

 large number of our common birds which are known to start breeding in April 

 and May, and have found that the glands reach their maximum size from a 

 week to a fortnight before the first laying of eggs takes place. When one 

 considers that the testes of small birds (e.g., House-Sparrow, Hedge-Sparrow, 

 Robin, and many others which I have examined) in January are only the size of a 

 pin's head (1 mm. greatest diameter), and in April or May, as the case may be, 

 reach the size of a small bean (average about 1'3 cm. in greatest diameter), it is 

 natural to suppose that if functionally active the testes of the Sanderling should 

 present correspondingly large dimensions at a corresponding period before the 

 female bird begins to lay. In this species the early clutches of eggs are laid 

 about the middle of June, the hatching-season lasting into July. Out of a 

 large series of testes obtained in May and June the greatest measurements did 

 not exceed 5 mm., 3'5 mm. being the average, while in Sanderlings obtained in 

 July the testes were still smaller, averaging 3 mm. in greatest diameter. 2 By early 

 August a further reduction had taken place in the size of the glands, and both 

 naked-eye and microscopical examination showed a marked similarity with the 

 testes of adult birds obtained in mid-winter. In the absence of knowledge as to 

 the size attained by the fully functional testes of the Sanderling, I have noted that 

 in those birds which show close affinities and come under the same family, viz., 

 Charadriida?, and are much about the same size as the Sanderling (Common 

 Sandpiper, Dunlin, Ringed Plover), the testes in May and June were double 

 the size of the largest testes of Calidris arenaria obtainable from my collected 



1 Vide British Association Report, 1909, p. 505. 



2 Even in many species which breed in April and May the full size of the 

 active testes is almost maintained in July. 



1910. T T 



