SECTIONAL TRANSACTIONS.— D. 559 



Miss A. M. Bidder. — Yolk Absorption in some Cephalopoda. 



In all Cephalopoda whose larval or embryonic forms are known, the development 

 is profoundly influenced, until an unusually advanced stage, by the presence of a 

 large mass of yolk. A portion of this yolk, which increases as development proceeds, 

 is contained in a yolk-sac within the animal. In Loligo (the type considered in detail) 

 it has been found that three separate methods are successively employed to absorb 

 this great mass of yolk. These methods are not constant throughout the group, 

 but show, in Sepia, interesting modifications, while Sepiola appears to be in this 

 respect intermediate between Sepia and Loligo. 



Reports of Committees. 



Afternoon. 

 Mr. E. R. GuNTHER. — The Plankton of a Sub-Antarctic Whaling Ground. 



The food of the ' Whalebone ' whales is planktonic, and that of the great Blue and 

 Pin whales has been shown in the south to consist almost entirely of one species of 

 Euphausian, Euphausia superba. A study of the plankton, therefore, is of great 

 importance in investigating the natural history of these whales. 



The Discovery 'Es.-pedition, in addition to carrying out, over the Southern Atlantic, 

 general plankton investigations which have shown this species E. superba to be confined 

 to the shallow waters of coast and islands, made an intensive plankton survey on the 

 ■tt'haling grounds. That at South Georgia is described and the provisional results 

 discussed. The Euphausians and the diatoms upon which they feed are shown to 

 have a somewhat curious distribution : the former concentrated in dense swarms on 

 the N.E. side and the latter in an encircling band round the island, having a maximum 

 density on the S.W. side. Chemical and mechanical causes are suggested to account 

 for this and the general richness of this whale feeding-ground. South Georgia is a 

 long island peculiarly placed at right angles to the west wind drift so that upwelling 

 of water rich in phosphates may give rise to the thick diatom growth which, carried 

 round either end, feeds the Euphausian ' Nursery ' in the sheltered water of the other 

 side. 



The general ecology of the plankton is briefly discussed. 



Mr. N. A. Mackintosh. — Discovery Expedition Work at Whaling Stations. 



The objects of making a systematic examination of whales at whaling stations are 

 first to procure evidence as to their specific identity and secondly to investigate the 

 reproductive processes and breeding habits. One thousand six hundred and eighty- 

 three whales, mostly Blue and Fin whales, were examined at South Georgia 

 and South Africa between February 1925 and April 1927. Work on their specific 

 identity will not be described at present, as the results are incomplete, but some 

 aspects of the breeding of whales can be described. The proportion of immature 

 whales is rather high, particularly among those captured o2 the .African coast. The 

 theory that breeding occurs mostly in the southern winter has been fully confirmed 

 and evidence from the reproductive organs and records of fojtuses point to June 

 and July as the height of the breeding season. The period of gestation in these 

 whales lasts slightly less than a year and the nursing period about seven months. 

 Whales probably become adult about two years after birth. The work has also 

 thrown some light on the distribution, movements and segregation of the whales. 



Prof. A. C. Hardy. — On the Unevenness of Plankton Distribution and the 

 Results of the New Continuous Plankton Recorder. 



Our knowledge of the density and distribution of the oceanic drifting life — the 

 plankton — is usually gained from samples taken at a number of distinct stations within 

 the area concerned. These stations, if the area is at all extensive, must necessarily 

 bo at considerable distances apart, so that we may doubt whether, owing to the 

 patchiness of the plankton, the samples give a true idea of its distribution. Experi- 

 ments have been made on the Discovery Expedition with a new instrument which 

 will give a continuous record, mile by mile to scale, of the plankton in the water 



