ToumS,May°!?°?m'] PROCEEDINGS OF SOCIETIES. 263 



Mr. Hogg said it occurred to him that it would be a very useful 

 and accurate test of the presence of albumen either in vegetable or 

 animal infusions. We want to know what substance, in conjunction 

 with the albumen, tends to impart this remarkable coloiu* in these 

 dichroic fluids. It would be of great value in medical investigations 

 if it could be determined by the spectroscope, whether in any par- 

 ticular fluid, say urine, albumen was present or not. 



Ml-. Slack thought that as Dr. Pigott's paper contained some points 

 of great interest, and that gentleman was not present to join in the 

 discussion, it would be better to defer the discussion for the present. 



Mr. Slack called the attention of the meeting to a series of micro- 

 scopic objectives made by Herr Gundlach, of Berlin, whose agent in 

 England was Mr. Winspear, of Hull). The Gimdlach objectives were 

 remarkable for combining a very considerable amount of merit with 

 unusually low price. The lower powers, 2-inch, 1-inch, 1^-inch, were 

 sold by Mr. Winspear at 17s., and -j-Vth and y^*^ immersion lenses at 

 3Z. 12s. 6d., including the Society's standard screw and brass boxes. 

 Mr. Slack said that in comparing the j)rices of competitors with those 

 of the great English makers it would be necessary to ascertain how 

 far the former were careful in maintaining that imiformity of quality 

 by which the best English glasses were characterized. It must also 

 be remembered that extraordinary skill was required to excel beyond 

 a certain j)oint. He was not able to state the exact limits of the 

 performance of Gundlach's -jVth and -j^th immersion lenses, but they 

 well deserved attention. A good form of student's microscope with 

 rotating stage by Mr. Winspear, and Gundlach's objectives was like- 

 wise exhibited. 



Mr. Hogg then read a paper " On Cercarise infesting Lymnteus 

 Stagnalis." 



Mr. Lee said he would mention a fact in confii*mation of what had 

 fallen from Mr. Hogg, resj)ecting the prevalent opinion that parasites 

 are imiversally a condition of disease. He had examined a great 

 many fishes on which parasites were found, and had found that gene- 

 rally these fish were in the best of health. A nobleman of his 

 acquaintance had recently told him of his experience in his fishing 

 expeditions in Ireland. He had caught several fine salmon, but as 

 some of them had parasites attached to them, his attendant, labouring 

 under the popular delusion, had thrown them back into the water, and 

 reserved only a few miserable fish on which parasites did not happen 

 to be present ; and he (Mr. Lee) took the opportunity of removing the 

 erroneous impression from the mind of his friend. This fact with 

 respect to parasites, he must mention, had relation to external parasites 

 only. 



Mr. Slack quoted the opinion of the distinguished naturalist. 

 Van Beneden, in reference to parasitism. The term parasite, he 

 (Van Beneden) says, can only be used when the creature lives uj)on 

 and is really detrimental to the animal to which it is attached ; and 

 unless this evident mischief results from their contact, the term 

 parasite cannot be properly applied. Mr. Slack then adduced some 

 instances of animals (such as the Meduste and Soldier Crab) which 



