(386 PHILOSOPHICAL TRANSACTIONS. [aNNO 1743. 



lar, which was one polypus that had fairly two heads, without any tail ; that is, 

 with a head at each end, as represented in fig. 1, pi. 18. This was an acci- 

 dental production, and as follows : two young ones grew, as from one root, 

 out of an old polypus, as in fig. 2. They both dropped ofF together, and their 

 tails not being separated, they appeared as in the first figure ; but, when I saw 

 them, more like fig. 3, with several young ones putting out from their sides. 

 Mr. Trembley said he had seen the like sometimes before, but not often ; and 

 that they have then remained 10 or 12 days in that condition, after which they 

 have separated. He had in one of his large glasses upwards of a hundred of 

 these insects all full-grown, and he regaled them all at once before me, with 

 some thousands of what he calls des pucerons d'eau, which are small aquatic 

 animalcules, not unlike fleas, of about the size of large ones, and which move 

 about with great swiftness in the water. These were no sooner put in, but it 

 was a curious and entertaining sight, to observe in how voracious a manner not 

 only every polypus, but every young one also that had arms, though fixed to 

 the side of its parent, seized and devoured these pucerons : and as the body of 

 the polypus is transparent, every one made a very extraordinary appearance, 

 from the number of pucerons in them ; for in several I could very plainly, with 

 my bare eye, distinguish and count 5 or 6 of them ; and I could plainly discern 

 some very small black spots, which I was assured were the eyes of these pu- 

 cerons. One extraordinary observation more of M. Trembley's is, that, in the 

 double-headed polypus of the 1st and 3d figure, there was at first but one com- 

 mon gut between them, so that the feeding of one head had the same ettect as 

 feeding them both. M. Trembley is particularly handy and dextrous in his 

 operations, and explains himself about them with great exactness and perspi- 

 cuity. He places some pieces of packthread across his glasses, towards the 

 top : to these some of the insects fix themselves ; and I have seen some that 

 in that position have extended their arms almost to the bottom, which must 

 have been above 10 inches. 



Of the Structure and Diseases of Articulating Cartilages, by fFilliam Hunter*, 



Surgeon. N° 470, p. 5M. 



The fabric of the joints in the human body is a subject so much the more 

 entertaining, as it must strike every one, that considers it attentively, with an 



* Mr. Wm. Hunter, afterwards Dr. Hunter, so celebrated as a demonstrator of anatomy, author of the 

 splendid plates of the gravid uterus, and founder of the great anatomical museum in Windmill-street. 



He was a native of Scotland, and (as his biographer Dr. S. Foart Simmons informs us) after some 

 years spent at the university of Glasgow, he was placed in the year 1737 in the family of Dr. CuUen, 

 who at that time practised physic and surgery at Hamilton. With him Mr. H. continued nearly 3 



