446 PHILOSOPHICAL TRANSACTIONS. [aNNO ISQI. 



where to have any connection or hold to it, but very readily dropped out, still 

 holding its liquor without spilling any of it. On repeated experiments of it in 

 this and other animals, it gave me opportunity to think, how it was possible this 

 humour could come into the inward bladder, without any cohesion to the out- 

 ward, which involved it. 



Secondly, observing them further by my naked eye, I perceived that to this 

 inward bladder there was a neck, or white body, more opake than the rest of 

 the bladder, and protuberant from it, but so as I could observe an orifice at the 

 extremity of it, which then to me seemed to be occasioned by the retraction of 

 some part of it inwards. By this I fancied it might, as by a mouth, suck the 

 serum from the outward membrane, and so supply its bladder or stomach. 



Thirdly, in this thought I was further encouraged by the assistance of my 

 very good friend Mr. Richard Waller, whose presence I desired at the dissection, 

 and by imparting to him my thoughts that these hydatides might be a peculiar 

 sort of insects, bred in animal bodies, we were resolved to satisfy ourselves of 

 the notion, and having observed what I have before mentioned, we found that 

 this neck, on approaching it to the candle, did really move, and that it did 

 protrude and then shorten itself. But for the more satisfaction, I shall give the 

 figures made by his ingenious hand ; both natural as they appeared to the naked 

 eye, and what they were discovered to be by the microscope. 



Fig. J, pi. )1, represents one of these watery bladders, in its natural size, 

 inclosed in its outward membrane or chorion ; its shape was almost round, only 

 flatted as a drop of quicksilver by lying on a solid. A shows the neck, seen 

 through the membrane ; which, in fig. 2, is more plainly represented, the out- 

 ward membrane being taken off, but still as appearing to the naked eye ; where 

 we observed an open orifice at the extremity of it, and that it is made up of 

 circular rings or incisures ; which, in fig. 3, being viewed by a microscope do 

 more evidently discover themselves ; this part is granulated with an abundance 

 of fine eminences all over. The orifice at the end seems here to be occasioned 

 by drawing itself inwards, and upon trial we found it so ; for, in fig. 4, is re- 

 presented the neck of this worm, drawn out its whole length, and magnified ; 

 where may be observed the lessening of the rings, and its tending to a point at 

 the end. And having opened it, within we found two small strings, A A, pro- 

 ceeding from the neck, and floating in the liquor. 



What these two strings may be, is hard positively to assert ; leaving others to 

 their own conjectures, I shall deliver mine : that this worm, by protruding its 

 neck, sucks from the outward membrane which involves it, and is furnished 

 with blood-vessels, the moisture or nourishment which is conveyed by these two 

 strings or pipes, into the stomach or bladder, and from whence, as tliere is occa- 



