43-2 RESPIRATION OF MESOGOMPII i'S- 



>uch as Oustalet, 1869, and ewu Scott. 1905, asserted that therr 

 were fifty thousand ^ills in a Lil)elluhd rectum. M\ i-ount> 

 reduce this somewhat. 



I mig'ht add that the greatest numlx-r nf re^piratf ir\ i)art> 

 — fields, g-ills, or vilh — in any form i> 4,800, the numher of vilh 

 in Ophiogoinj^hus. C'(»imtino- all the folds, we i;et onl\- 24O for 

 Mcso()Oiii/^liiis. Anas has ahout 1.900 villi, and the other forms 

 with villi a like number. The forms with folds never show over 

 300 folds. 



A point of special interest in the case of Mesogompluis is 

 that its gill-folds are apparently the most primitive form of gill 

 found in dragon-flies. With this as a centre, we can proceed 

 to all the ifoniis of gill. One line, with slight change in form 

 of buttress fold, leads to Auax, 1 ia Aeslimi. and Corditlcijaster. 

 [ndependentlv there seeiu to ha\e arisen at two points on this 

 line of evolution villi. The \illi of Goiiipliiis and Hiu/ciiiiis are 

 >o different from those of Anas that we may safel}' consider 

 them as mori^holcjgically dissimilar. ''^ Another line, leading from 

 Mcsof/oiiipliits, leads directly to the Lil)ellulidce, by supi)ression 

 of the huigitudinal folds. When we consider that the experts 

 Mil dragon-flies, such as Needham, Ris, etc., hold that the dom- 

 phime are the starting'-point for the e\-olution u\ the more 

 ^pecialised forms, we see this statement conflrmed. The rec- 

 n\u of the nymi:)h of Mesofjoiiiplnis gives tis the most primitive 

 K-novvn form of that part as a respiratory organ. 



(Read July 7, 1917.) 



"R.WSACTIONS UV SOCIEII KS. 



SuCTH .\fric.\x rxsTiTUTK OF Kij'XTRUAi. ExciXEKKS. — Thursday, 

 February 2isl: Prof. J. H. Dob^on, D.S.O., M.Sc, M.Eng., M.I.Mech.E.. 

 VI.I.E.E., A.M.r.C.E., President, in the chair.— " T/r Industrio! Awaken- 

 ing of -the ik'iir: Soiifli .Ifriaiii drvdopmenl '' ( ['residential address): 

 Prof. J. Fl. Dobson. Attention was drawn, in the first i.>art of the 

 :iddress, to the industrial research and investigation undertaken in Great 

 P.ritain during the v)friod since the outbreak of \v;u', particularly in con- 

 nection witii the Fuel Researcli IJoard and the Coal Conservation 

 Connnittee. Ihe eft'ect of war conchiions on South Africa was then 

 referred to, and the compensating advantages, resulting in improvement 

 in internal trade and the birth of new industries witliin the Union, were 

 pointed out. Allusion was made in particular to the country's coal 

 resources, to certain possibiHties of water power, and scb.enies of power 

 supply and distribution, to the question of liquid fuel, to the prol)lcin of 

 transport and the prospects of some base metal industries. 



South African Institltiox of Excixfkks.— Saturday, March yth : 

 G. M. Clark, M.A., AI.I.C.E., President, in the chair. — "A short note on 

 types of induction motors": T. W. Kirkland. The paper described 

 briefly the leading features of various tj-pes of induction motors, and 

 directed attention to their relative advantages and disadvantages. 



* See Ris, 1913. 



