MIGRATIONS OF NEMATOID LARVA. 313 



this, he took a number of very small caterpillars of the small 

 ermine moth which had just been enticed out by the spring sun, 

 and threw thirteen specimens of these caterpillars, which, as he 

 had ascertained by the microscope, contained as yet no young 

 thread-worms upon a watch-glass containing moist earth from 

 the above-mentioned flowerpot, in which, as he had convinced 

 himself, lively young of the matured thread-worm {Mermis 

 albicans) occurred. In 18 hours 5 of these caterpillars con- 

 tained embryos of Mermis. In a second experiment, made in 

 the same way with 33 caterpillars, there were, in 24 hours, 14 

 individuals with embryos of Mermis; each of these caterpillars con- 

 tained 1, and 2 of them even 3 embryos. In experiments made 

 in the same way with the caterpillars of Pontia Cratcegi, Liparis 

 chrysorrhcea, and Gastropacha neustria, the same result also 

 occurred. On the day after the experiment, embryos of Mermis 

 were found in 10 out of 12 such caterpillars; 5 of them con- 

 tained 2, and 1 even 3 embryos. (Vid. Von Siebold iiber 

 die Band- unci Blassenwurmer, nebst einer Einleitung iiber die 

 Entstehung der Eingeweidewurmer, pp. 9 — 12. 1 ) Still more 

 interesting are the results which Meissner has obtained with 

 regard to the migrations of the Gordii, and from their im- 

 portance in relation to the theory of the production of Trichnice, 

 I shall refer to them further on. From what has just been said, 

 and from what we shall mention hereafter, about the Trichinae, 

 we may certainly come to the conclusion, that " many Entozoa, 

 and certainly those which remain parasitic in their last, i.e. sexually 

 mature stage, do not migrate into the animal appointed for their 

 habitation, in order to become further developed in it, until they 

 have elsewhere attained a certain development and bulk." (Vid. 

 Von Siebold, 1. c, p. 13.) 



Amongst the round-worms of the human subject, the brood of 

 Filaria medinensis may, perhaps, behave most like the Nematoida 

 just referred to. It is true that in the other human Helmintha 

 we have not yet seen an exclusion of the brood from the egg- 

 shells when laid in water : it is true that such an exclusion 

 would be necessary if the brood of Filaria should enter the body, 

 as is generally supposed, by adhering to the feet of those men 

 or animals that wade in marshy or stagnant water ; but we 

 know, at least from Malgaigue and Robin, that the brood lives 



1 Translated into English, and published with this volume. — [Trans.] 



