48 Excerpt a Zoologica : — Entozoa. 



to some of the readers of the e Annals ' as to myself, and have 

 therefore put them into English in order to place them at 

 your disposal. 



As many of the extracts may have a relation to papers pre- 

 viously published, but which have not been taken notice of in 

 this country, I will endeavour to select some few passages 

 which will bring the information on the subjects of which they 

 treat down to the date of the notices communicated. 



Yours truly, 



Soley Terrace, Pentonville. yy FRANCIS, Ph. D. 



Entozoa. 

 The observations on intestinal worms are becoming daily more 

 numerous, and all tend to show decidedly that there are yet many 

 profound and dark mysteries, especially with regard to their meta- 

 morphoses and migrations, which have still to be unveiled. 



Eschricht in a valuable memoir ■ On the Origin of Intestinal Worms,' 

 wholly rejects the notion of a generatio cequivoca, and maintains that 

 intestinal worms originate in every case from individuals of similar 

 genera ; otherwise for what purpose would be the immense masses 

 of eggs and young in the Ascarides and Tape-worms ? In what form 

 the intestinal worms find their way into other animals, it is not yet 

 possible to say ; but, as an answer to this question in part, it is very 

 important to know that these creatures have recently been observed 

 to undergo metamorphoses and to change their locality : we know 

 of Ligula and Bothryocephalus solidus, that they only thrive and de- 

 velope perfectly when they have passed from one animal into an- 

 other. The observation that many fish have worms in their flesh 

 only at certain periods of the year, seems likewise to indicate such 

 migrations among Entozoa*. Eschricht moreover regards, as of 

 much importance, the question whether worm-diseases are conta- 

 gious, as an explanation of the manner in which the contagion takes 

 place can only be attempted when such is ascertained. 



M. Streckeisen has communicated to the Naturalists' Society of 

 Basle a notice in which he states that he had observed the number 

 of Entozoa in the intestinal canal of several animals to decrease with 

 the commencement of winter, and was thence led to conclude that 

 most intestinal worms are annual, dying off towards winter, and 

 being subsequently reproduced by eggs. This observation agrees 

 perfectly with those of Eschricht, and we are now able to assert that 

 the various periods of the year exercise an essential influence on the 

 increase and decrease of Entozoa. 



Prof. Mayer in Bonn (Mull. Archiv, 1842, p. 212. pi. 15.) found a 



* In Copenhagen, for instance, it is a common saying that no cod is fit 

 to eat in those months which have no r in them, as their flesh then con- 

 tains worms. Eschricht examined Gadus Callarias frequently in the months 

 of May, June, July and August, and found Echinorhynchi in their flesh. 

 Bearing in mind these facts, and the discoveries of Miescher, which will be 

 subsequently communicated, there can scarcely be any doubt as to the mi- 

 grations of the Echinorhynchi. — W. F. 



