SECTIONAL TRANSACTIONS.— D. 333 



intervals (about once a minute), but in a larva taken from a vigorous culture and 

 examined immediately it may occur forty times a minute. 



The dorsal sac is derived from the posterior tip of the right anterior ccelomic 

 sac ; it has the origin and the position of the so-called pericardium in Balanoglossus. 

 The heart of Balanoglossus is like that of Echinus, a blastoccelic space contained 

 between the ventral wall of the pericardium and the dorsal wall of the oesophagus. 

 Peristalsis, as in Echinus, is directed forward. This pulsating vesicle is already 

 developed in the Tomana larva and affords another proof of the homology of the 

 Tomana and Echinoderm larva;. 



Lt.-Col. the Right Hon. Sir Matthew Nathan, P.C., G.C.M.G., Sir T. W. 

 Edgeworth David, K.B.E., C.M.G., D.S.O., F.R.S., Mr. F. A. 

 Potts, and Dr. C. M. Yonge — The 1928 Great Barrier Reef Expedition. 



Sir M. Nathan. — Prior to 1922 inquiries with regard to the reef in its various 

 scientific aspects suffered from want of continuity and of correlation ; in that 

 year a committee of Australian scientists was formed to secure continuous and 

 related investigations ; under their direction some physiographic al and geo- 

 logical work has been done ; owing to want of trained biological investigators 

 and to other reasons, biological inquiry of a systematic and comprehensive nature 

 has not yet been started ; and the Australian Committee is hoping to get such a 

 start made by British investigators with Australian assistance. The keeping of 

 continuous records of biological interest and possibly even the establishment on a 

 permanent basis of a Marine Biological Station in the south-western Pacific may, it 

 is thought, be the ultimate result of such an expedition. 



Sir Edgewokth David, in stressing the importance of sending a well-found 

 zoological expedition to work on the Great Barrier Reef of Australia, emphasises 

 (1) the need for determining the existing bathymetric life zones in the present reef 

 for comparison with the zones in the core from the recent diamond drill bore through 

 the reef, near Cairns, in Queensland ; (2) the general scientific importance of further 

 exploring the Great Barrier Reef, especially from the point of view of the recently 

 advanced theory of the post-glacial origin of existing coral reefs throughout the 

 world. 



Mr. J. Gray. — The Evolution of the Vertebrates from an Experimental 

 Point of View. 



The course of evolution must have conformed to the principle of physiological 

 continuity of function as well as to morphological continuity of structure. The 

 bearing of experimental methods on such problems is illustrated by the data derived 

 from the eggs of aquatic and terrestrial vertebrates. 



The transition from aquatic to completely terrestrial life can only have occurred 

 in those forms which were physiologically equipped with a mechanism for providing 

 the embryo with an adequate supply of water. One half of the weight of a newly 

 hatched fish consists of water derived from the external environment ; more than a 

 half of the water in a newly hatched chick is derived from the albumen. These facts 

 suggest that the Amniota are to be derived from a form whose egg was similar to those 

 of modern Dipriocus or Amphibia in that it possessed a tertiary gelatinous capsule. 

 This capsule was primitively of a protective function, but was utilised as a reservoir 

 of water as soon as the eggs were laid on land. The modern Amphibia provide a 

 series of types whose eggs are physiologically intermediate between those of a typical 

 fish and those of a typical Reptile. The reserve of water in Monotreme eggs is of a 

 different type from that of Reptiles, and in the reduction of the albumen layer the egg 

 foreshadows that of Eutherian mammals. 



Mr. C. F. A. Pantin. — Movement in Amoeba. 



Although Amoebas may be considered degenerate rather than primitive, yet in 

 their movement they exhibit the most generalised form of contractility to be found. 

 There is a great variety of types of amoeboid movement, but they all agree in that, 

 unlike muscle and cilia, the amoeboid individual possesses no permanently differentiated 

 contractile structures. 



