1904-1905] Report of the Microscopical Section. 225 



REPORT OF THE MICROSCOPICAL SECTION. 



By Mr W. C. CRAWFORD, F.R.S.E., Convener. 



The Microscopical Section met regularly twice a - month 

 during the winter session, each meeting occupying nearly 

 three hours. The meetings were well attended and enthusi- 

 astic. We were again fortunate in having, as demonstrator, 

 Mr Staig of the Natural History Department of the University 

 of Glasgow, and the Section studied zoological siibjects. We 

 began with the earthworm; and after spending a couple of 

 evenings over it, we devoted attention to several other worms, 

 free and parasitic. That great group of animals commonly 

 spoken of as Worms shows well how organisms on a common 

 plan adapt themselves to very different conditions of life, — 

 frequently to marvellous environments. From the free plan- 

 arians we proceeded to the liver-fluke {Distonmim hepaticum), 

 and studied its structure. It has no heart and no blood, and 

 it directs itself to the organs in the host where the most 

 nutritive food is to be found. In course of time, and by 

 regressive evolution, it will probably be able to do without a 

 mouth : in that case the mouth will disappear. Every organ- 

 ism, to speak anthropomorphically, tries to live as easily as it 

 can, and when it is prevented from accomplishing that, it may 

 rise to higher things. Amongst men we have the almost 

 universal approval of cheapness and disregard of its effects on 

 the social organism. We had a very pretty demonstration of 

 that large parasitic nematode, Ascaris. As usual, our pro- 

 cedure had three stages : we dissected the worm first ; then 

 we examined parts of it microscopically ; and finally, we 

 philosophised about what we had seen. Parasitism is associ- 

 ated with regression, but every young mammal is a parasite at 

 first, though the parasitism here is only temporary. 



Then we examined some curious Arthropods, amongst others 

 the so-called skeleton screw (Caprella), with its gymnastic, at- 

 tenuated body, and the parasitic Sacculina, become by degenera- 

 tion almost a tumour. We had an example of the curious 

 Phronima, which lives commensally in the body of a pelagic 

 tunicate ; and we spent some time over that most interesting 



