SOUTH \I"KJ(A\ SNAILS. 3/7 



In each 'Distance, the parasites migrate to the snMllest blood- 

 vessels that can accommodate them. In this way the female 

 comes as close as possible to the exterior, when laying her eggs, 

 2vithont herself leaving the biood-strcani. 



Unlike the smaller parasites of the blo-od-stream, reproduc- 

 tion of the Schistosom.e group can take place only outside the 

 hlood-streani, and by means of a fresh-water mollusc as the inter- 

 mediary host. 



( Read, July lo, iyi8. j 



TRANSACTIONS OF SOCIETIES. 



Geological Society of South Africa. — Thursday, March 21st: .\. L. 

 du Toit, B.A., D.Sc, F.G.S.. President, in the chair. — ' The zones of the 

 liarroo sysloii and tlicir distribmion " (Presidential address): Dr. A. L. 

 Du Toit. The address outlined the advances that have been made during 

 the last fifteen years towards the detailed stratigraphy of the system, and 

 was devoted mainly to the distribution of the Karroo System in tlie 

 eastern and south-eastern part of the Union. 



Monday, April 15th : J. J. Garrard, Vice-President, in the chair. — " On 

 the mode of occurrence and distribution of asbestos in the Transvaal " : 

 A. L. HalL The earliest asbestos workings in the Transvaal were com- 

 menced east of Carolina, about 1906, and were carried on at intervals 

 until 1914. Recently extensive deposits of asbestos have been found in 

 the Lydenburg district and east of Chuniespoort : the establishment of a 

 flourishing industry, with every indication of permanency, gives promi.se 

 of being realised- The author therefore placed on record the geology of 

 of the principal occurrences of asbestos, with special reference to the more 

 recent discoveries which differ in several respects from the Cape Province 

 deposits. — " Cortindum of the Zoutpansberg fields and its matrix": Dr. 

 P. A. Wa^er. South Africa is at present the leading corundtun- 

 producing country, the rate of production being about 400 tons per month. 

 The greater part of the output is yielded by the Zoutpansberg and Pieters- 

 burg districts of the Transvaal. Most of the corundum recovered is in 

 the form of loose eluvial crystals, a much smaller proportion being boulder 

 or rock corundum. These two types of corundum were separately 

 descrilied. 



Tuesday, July gth : D. Wilkinson. Vice-President, in the chair. — "On 

 certain felsitic rocks hitherto called ' banded ironstone ' in the ancient 

 schists around Gatooma. Rhodesia" : A. E. V. Zealley. The nature 

 and origin of a widely distributed rock, commonly referred to as 

 "handed ironstone." was explained. Investigation of these rocks in the 

 field points definitely to a large part of them being felsitic rocks, that is 

 to say they are nf igneous origin, and not aqueous sediments. — " Plunia- 

 site (corunduni-aplite) and iitanifcrous magnetite rocks from Xatnl": 

 Dr. A. L. Du Toit The author described certain deposits of corundum 

 in the Tugela Valley that are of particular interest in adding to the long 

 list of different ways in which this mineral can originate. In the second 

 part of the paper an account was given of some titaniferous magnetite 

 rocks carrying silicates and spinel that occur in the same neighbourhood 

 as magmatic "segregations" within a philonic body ranging in character 

 from a gabbro to a pyroxenite. 



South .African Tnstitctk ok Elec'trical Enginf.ers. — Thursday, 

 March 21st : J. W. Kirkland, M.Am.I.E.E., Past President, in the chair. — 

 "Small generating stations and electricity supply schemes" : R. F. 

 Botting. The paper dealt with municipal schemes for the supply of 

 electricity for lighting and power in the .'^mailer towns of the I'^nion, and 



