INTESTINAL WORMS. 173 



larvaB, Cercarice, from the larval state to be changed into pupae, and 

 from this finally to become Distomes 1 . 



Besides these changes of Distomes, of which the entire series, in 

 its chief features at least, has been investigated, there are others 

 relating to Tcenice which [until lately] were only observed frag- 

 mentarily. Such was that of LEBLOND, who found in the peritoneum 

 of Murcena conger a worm enclosed in a cyst and containing a 

 young Tetmrhynchus. He described this larva of Tetrarhynchus as a 

 species of Amphistoma and the Tetrarhynchus as its parasite 2 . MlES- 

 c HER also made similar observations. Sometimes the successions of 

 development appear to be possible only on change of abode. The 

 simple Ligulce of fishes are found, according to KUDOLPHI, in birds 

 that feed on fishes in their more perfect form and furnished with 

 developed sexual organs : the worms of the [supposed] genus 

 Scolex, that live in Pleuronectce, are probably changed in the bodies 

 of Kays and Sharks into Bothriocephali, and the Bothriocephalus 

 solidus, that lives in Gasterosteus pungitius, is changed, according to 

 ABILDGARD S and CREPLIN, into the Bothriocephalus nodosus of water- 

 birds (Mergus, Colymbus, &c.), which feed on that fish. That worms 

 should thus continue to live in other animals becomes less surprising 

 when we consider their tenaciousness of life; Ligulce have been 

 found alive in under-cooked fish ; RUDOLPHI found individuals of 

 Ascaris speculigera stiff and hard in the gullet and stomach of a 

 Cormorant that had been kept for eleven days in spirit of wine 

 which returned to life in warm water : and MIRAM saw individuals 

 of Ascaris acus from the Pike dry and sticking to a board revived 

 by water, and in some instances moving a part which had imbibed 

 the fluid whilst the rest continued shrivelled up and adhering im- 

 moveably to the board 4 . 



These observations prove, by the way, that it is not necessary 

 to have recourse to equivocal generation in all cases of Entozoa 

 where their existence appears to be inexplicable by the ordinary 

 mode of propagation. 



[Tape-worms attain their full development and mature sexual 





1 See STEENSTKUP Alternation of Generation. 



2 Ann. des Sc. not. sec. Se'rie. Tom. vi. Zool. pp. -289 295, pi. \6, f. I 5. 



3 EUDOLPHI Entozoor. Hist. Nat. n. P. n. pp. 60, 61. 



4 WIEGMANN'S Archivf. Naturgesch. 1840, i. s. 3537. 



