TRANSACTIONS OF SECTION D, 41D 



It was found by a long series of measurements of the combs of hens, that the 

 combs are continually fluctuating in size, the fluctuations being exceedingly 

 rapid and between very wide limits, a comb increasing or decreasing to as much 

 as 200 per cent, of its area in three weeks. It was found that the rapid increase 

 of the comb invariably takes place just before a period of egg-laying begins. 

 An examination of the structure of the hen's comb shows that it is composed 

 essentially of two walls of fibrous and vascular connective tissue between which 

 there is a loose core of connective tissue which at the period of egg-laying 

 becomes infiltrated with fat, and this rapid fat-infiltration is the cause of the 

 sudden increase of the mass of the comb. Now this fat- infiltration and increase 

 of the comb takes place when the ovary is storing up large quantities of yolk, 

 i.e., at a period when large quantities of fatty material are being conveyed in the 

 blood to the ovary. We have therefore an instance of a simultaneous effect upon 

 the ovary and a secondary sexual character brought about by the presence of 

 an excess of fatty material in the blood. This is probably analogous to what 

 happens in Sacculina and Inachus. 



19. The Effect of Sacculina upon the Fat-metabolism of the Crab Inachus 

 mauritanicus. By G. C. Robson. 



These observations were undertaken to extend Geoffrey Smith's theory of the 

 Sacculina acting as a stimulus for the production in the host-crab of a yolk- 

 forming substance similar to that developed in the normal 9 at sexual maturity, 

 which substance conditions the appearance of the secondary sexual characters. 

 Heim's observations on the blood-lipochrome of various Decapoda. Importance 

 of these to the theory of Smith. The blood-lipochromes of Inachus. Their 

 behaviour and occurrence in normal, moulting, and infected crabs. Their relation 

 to the fat-metabolism. The Decapod liver as a fat-storing organ — in normal, 

 moulting, and infected animals. The origin of the fat supply in relation 

 to infection by Sacculina. The destination of the fat of moulting, sexually 

 mature \ and infected crabs. The ultimate fate of infected crabs. Main con- 

 clusions : — 



(1) The infection by Sacculina induces the maintenance of a quantity of fatty 

 substance in its host's liver and blood, more constant or more excessive than 

 under normal circumstances. 



(2) This condition resembles that found in normal <j> and J preparing to 

 moult, and in sexually mature ? ; the ultimate destination of the fat being func- 

 tionally similar in the case of the mature ? and the infected crabs. 



(3) In all probability the fate of infected crabs is death from starvation owing 

 to their inability to obtain enough fatty material for their own immediate needs. 



20. On the Experimental Control of Dominance in Echinoderm Hybrids. 



By H. M. Fuchs, B.A. 



In 1909 and 1910 D. H. Tennent, working atTortugas, crossed Hipponde J x 

 Toxopneustes ? , and Toxopneustes <? xHipponde ?, getting in both cases larvae 

 with a preponderance of Hipponde characters. By keeping the eggs in sea-water 

 with increased and decreased concentrations of OH ions during the segmentation 

 period, he claims to have altered this dominance. A decrease of OH ions gave 

 Toxopneustes characters. The skeletal characters were used as criteria, the most 

 important being the presence of fenestrated rods in the postoral arms of Hip- 

 ponde and of simple rods in Toxopneustes. Tennent said, 'I shall regard the 

 presence of more than one rod in the postoral arms as an indication of Hipponde 

 influence.' Now it is well known that pathological larvae always tend to grow 

 extra rods in the arms, and a large number of Tennent's figures show irregular 

 shapes. He points out that his controls did not show multiple rods, but these 

 were not in an abnormal environment. The decrease of OH ions may have 

 swung the dominance to the Toxopneustes side, or it may have had a directly 

 pathological effect on the hybrids. 



At the suggestion of Dr. Cresswell Shearer, the author repeated Tennent's 



