Wellington Philosophical Society. 457 



doctrine of causation, that "difference" and "constant conjunction" 

 between two phenomena " are all the circumstances that enter into the idea 

 of cause and effect." The truth rather was that we never wholly under- 

 stood the causal connection between two phenomena till we perceived the 

 identity between the cause and the effect. In illustration of this he cited 

 a passage from Spinoza on the efficient cause of a circle. 



2. " On the Occurrence of Morchella esculenta," by T. Kirk, 

 F.L.S. 



Abstract. 



This paper recorded what the author believed to be the first discovery 

 in New Zealand of the true Morchella esculenta, a valuable edible fungus. 

 The specimens described were collected near Otaki by Mr. C. W. Lee ; 

 but it is decidedly rare. The author mentioned that the reported occur- 

 rence of this fungus in Canterbury by Mr. Armstrong is evidently a mistake, 

 the specimen from that district being M. cornica. 



Mr. Travers said he had found this fungus in New Zealand some 

 eight years ago. It commands a high price in Paris, and if it could be 

 jn - ocured in quantity would prove a valuable source of revenue. 



Sir J. Hector believed that it had been found in the Upper Hutt 

 District. 



3. " On the Hessian Fly," by W. M. Maskell, F.E.M.S. 



Abstract. 



The identification of the wheat fly sent down from the Eangitikei District 

 with the true Hessian fly (Cecidomyia destructor) is a matter of some 

 importance. The larva, or maggot, answers entirely to that of C. destructor, 

 possessing the peculiar appendage beneath the head, called the breast-bone, 

 characteristic of the Hessian fly. The author had, at first, some doubt as to 

 the veining of the wings, but has since been able to satisfy himself that the 

 real Hessian fly has reached these islands. The Hessian fly is, however, 

 subject to much damage from the attacks of other insects — parasites as they 

 are called. The author reported that in New Zealand it had no sooner 

 arrived than it was attacked by parasites in the form of hymenopterous 

 insects, probably of the family Proctotrupidce, and indigenous to New 

 Zealand. 



Exhibits. — A specimen of the " bladder fluke" obtained from 

 a rabbit captured at Dry Eiver, Wairarapa, by Mr. Coleman 

 Phillips, was exhibited by Sir James Hector. 



The speaker raid that this was one stage of the tapeworm of the fox, 

 wolf, etc., and probably of the wild dog and cat. He further stated that 

 in America he had seen large tracts of country cleared of rabbits in a few 

 months by the propagation of this disease. This is the third time the 

 disease has appeared in the Wairarapa ; but the difficulty in this country will 

 probably be to secure a proper host, as otherwise the worm cannot reach 

 maturity, and the disease will die out. 



