PROCEEDINGS OF THE SOCIETY. 689 



Mr. A. D. Michael said that the account which Mr. Deby had given 

 of the Dipterous insect was of very great interest ; the point which 

 struck him most being the kind of parallelism shown to what was found 

 in the case of some of the Calcidldfe. Most of the members of this 

 family were free-flying creatures, but from the fact of many kinds acquir- 

 ing running habits the wing power had been lost, the organs becoming 

 small and feeble. The degradation of the wings in the specimens shown 

 might probably be due to a similar alteration of habits. With regard 

 to the peculiar foot, there were one or two instances of a similar kind 

 found amongst the outlying groups of the Diptera, which were chiefly 

 parasitic, where, between the properly developed claws, the sucker had 

 been modified into a comb-like structure, which was very curious, and 

 was certainly an approach to that shown in the specimen exhibited. 



Prof. Stewart said they had a familiar example of the reverse of this 

 process in cases where the comb-like structure was the usual form in the 

 case of some of the spiders. Usually amongst spiders there was a claw 

 deeply toothed in the manner so well known to all who had examined a 

 spider's foot, but in the case of the hunting spiders this had been 

 developed into a sucking foot. 



Mr. Crisp read a letter from Mr. Enock, in which he said that having 

 succeeded in tracing out the life-history of the Hessian fly, he hoped to 

 be able to exhibit a complete set of slides at the meeting. 



Mr. Enock said that having unfortunately spoilt one of the slides, he 

 was unable to show a complete series that evening ; he hoped, however, 

 to be in a position to do so on a future occasion. He had bred both the 

 American and the Russian species to see if they were the same as those 

 found in this country, but he found that whilst Dr. Eeinsman (?) said 

 they laid from 80 to 100 eggs, the first specimen he bred laid 158 eggs 

 on a stalk of barley. He had spent a great amount of time in watching 

 the transformation of the fly, which emerges generally between 4 and 5 a.m., 

 though he had found them in the act soon after 3 a.m. 



Mr. Crisp called attention to two slides which had been sent by Mr. 

 Cole, and asked Prof. Stewart to describe them. 



Prof. Stewart said that the first of these was a section of the eye of 

 a newt, which showed most of the features of the retina, and at the same 

 time the general relations of the other elements of the eye. The other 

 slide was a section of the head of the human embryo, a thing always 

 difficult to obtain, especially in a sufficiently fresh condition for cutting 

 sections of much value. This slide was labelled as showing the 

 primary and secondary optic vesicles ; this however was a slip, because 

 it was not possible for these to be seen at the same time. Prof. Stewart 

 then, by means of drawings on the blackboard, described the process of 

 development of the eyes in the embryo, and showed the difference 

 between the primary and secondary vesicles with their relation to the 

 ultimate structure of the organs. 



Mr. Badcock said that he had the pleasure on one or two occasions 

 of calling attention to a pond which in all his experience of collecting 

 was the most extraordinary he had ever found, in consequence of the 

 rarity of the forms and the variety to be obtained from it. Dr. Millar 

 had asked him more than once to write a paper or to make a cata- 



