102 DEVELOPMENT OT 



with hooks, was deeply retracted within the animal, and 

 which after some time it began to extend,- and finally 

 protruded as its armed proboscis (fig. c.) Whether the 

 animal lay in this cyst as in a ßort of pupa condition, I 

 I must leave undetermined, but such appeared to be the 

 case. This observation corroborates the opinion of Prof. 

 Eschricht, that the Ecliinorhynclii probably penetrate the 

 fish ; for he found in the summer months, in the flesh 

 of the Copenhagen haddocks numerous Echinorhyncld 

 which he could only regard as young ones, in the act of 

 passing through the skin and flesh to the intestinal canal, 

 their proper abode, and in which situation only, are they 

 met with, as adult, or nearly adult individuals, so that 

 the helminthologist Siebold has never yet met with 

 Uchinorhpichi so young, that the so-called " loose ovaries" 

 were not developed in them, and has never even met with 

 individuals which he could altogether call " small,''"^" on 

 which account the encysted individuals mentioned above 

 as occurring in the abdominal cavity, are not without 

 interest. 



Lastly, with respect to the metamorphosis of the 

 Cestoid worms, we have an example of it presented to 

 us in Miescher's interesting memoir f on the forms which 



* Tide Burdacli's Physiologie, 2d edit. torn. ü. 



f I am acquainted "witli tkis memoir only througli tlie reference to it made 

 by Siebold ia the Report of Contributions iii the province of Hehninthology 

 during the year 1840, given ia Erichson's Arcliiv, 1841, s. 301-304; but 

 I must remark, that it is rather bold to assume that the encysted Mlariae 

 piscium are transformed into clavifonn cysts, wherein is found at first a 

 trematode animal, which is afterwards developed into a Tetrarhynchus.. These 

 encysted FilaricB piscium, which occur so abundantly in the haddock, &c., and 

 whose description by Siebold has already been once mentioned in this memoir, 

 betray, as it appears to me, but very little shnilarity with the at first tubular, 

 afterwards clavate cysts wliich I have found loose in the abdominal cavity 

 and on the viscera of Esox belone, and Avithin which there is always a Te- 

 trarliynclms, with spu-aUy contracted hooked tentacles, capable of being ex- 

 tended to an extraordiuai'y length. The earher condition, so far as I have 

 been able to judge of the fuhe, certainly has the form, but none of the struc- 

 ture of a Filaria. The contracted ammal inclosed in the knob-Hke cysts in 

 which the Tetrarhynchus is developed, resembles, as far as its substance is 

 concerned, a very young cestoid embryo. All the developed Tetrarhynchi 

 witliin the cysts had the appendix to their bodies which is mentioned by 

 Miescher as being present m those which he met ivith in the cavity of 



