218 PROCEEDINGS OF SOCIETIES. 



wliich had been afforded to him of examining this parasite, the genetic 

 relations of which, though obscure, were full of interest to those who 

 j)ursued this department of science. 



The President, alluding to Mr, Hope's memoir " On Sewage Irri- 

 gation," asked Dr. Cobbold what were his views on the subject, specially 

 in regard to the paper. 



Dr. Cobbold replied, briefly stating that the British Association Com- 

 mittee having invited him to inspect an animal fed on Mr. Hope's farm 

 on sewage-grown grass, he had carefully examined the animal, and had 

 not foimd a single j^arasite of any description in it ; whereas in the ox, 

 under ordinary circumstances, one would expect to come across one or 

 more of the score of different species liable to infest that ruminant. 

 Here, however, there were none. But although this fact was, as far 

 as Mr. Hope was concerned, an agreeable one, it did not, he thought, 

 alter his (Dr. C.'s) original position in regard to the question, because 

 it so happened that Mr. Hope's farm was a perfect model of what a 

 sewage farm ought to be ; and because the soil, being very porous, was 

 eminently favourable for taking iu any germs that might hajipen to be 

 in the sewage. The case, however, was exactly the reverse on the 

 Croydon farms, where there was a j)estilential swamp, on which the grass 

 was covered with deposits, and where eggs must inevitably be jDresent if 

 such eggs existed in the sewage. And though some people thought that 

 because those eggs had not been found in the sewage after it had been 

 distributed, no eggs were there ; he asserted that millions of ova of 

 entozoa were passed by persons in this metropolis, and it followed that 

 numbers of those entozoa must find their way into the sewers, and be 

 thence conveyed to the fields. To the question. Are ova carried like- 

 wise ? the only answer that could be given was, that the common mode 

 of the j)ropagation of germs of entozoa must be through those channels, 

 for they could go through no others ; and under ordinary circmn- 

 stances the eggs must go into the animal feeding upon the sewage- 

 grown grass. His original statement therefore as to the mode in 

 which the germs were sj)read abroad tvas not overthrown. The 

 animal exhibited by Mr. Hope had been so carefully tended and 

 reared, that it was next to impossible that any ovum could be brought 

 into contact with it ; and indeed the assiduous care bestowed upon it 

 had served to deprive the animal of the privilege of harbouring even 

 those parasites which would otherwise have been found in the body. 



The President read a paper " On the Form and Use of Facial 

 Arches in the Salmon." 



Mr. H. Lee asked the President at what stage or period of the 

 development of the embryo salmon the " blow-holc-like " organ which 

 it was known did not exist in the adult fish was obliterated and ceased 

 to be perceptible. 



The President said, in the specimens of embryo salmon which he 

 had examined he had been able to get at a very early stage in which 

 he could discern a flat white band going round the yelk, and one eye- 

 speck was visible. Before hatching he got two more stages, and in 

 the second stage the ear-opening or spiracle became obliterated. 

 There was a great difference between the salmon and the frog, for 



