DEVELOPMENT OF THE NEMATOLDA. 311 



asexual, and therefore their species difficult to determine; this 

 condition is only changed by other favorable circumstances, 

 and the animals thereby carried on towards their development. 

 Lastly, it is certain that the embryos of the nematode worms 

 may pass the winter in a sort of torpid state in the open 

 waters. 



When Verloren set free the embryos artificially by crushing 

 the eggs, they soon died, partly stifled by the fungoid structures 

 growing about them, and partly from their becoming the seat 

 of fungoid growths. 1 Independently of Verloren's investiga- 

 tions, and at a period when the experiments of that savant could 

 not have been known in Germany, H. E. Richter, of Dresden, 

 had also put the eggs of an Ascaris lumbricoides into water 

 (on the 15th November, 1854). The eggs, which were all 

 without living embryos, and which had not even exhibited 

 globules of segmentation, were not examined by Richter for 

 some time after their being placed in water; but on the 15th 

 October, 1855, (consequently after the lapse of eleven months,) 

 he found living embryos in all the eggs, of which he sent a 

 considerable number to Haubner, Leuckart, and myself. These 

 were employed in experiments, which unfortunately furnished no 

 result. 



When I examined dry eggs of the same worm, which Richter 

 had sent to me, I had only the opportunity of confirming 

 Richter's statement, that on the 15th November, 1854, the eggs 

 had hardly commenced any development. 



All this shows that a portion of the eggs of the nematode 

 worms issues, in the first instance, passively from the body of 

 their previous host into the external world, and first of all passes 

 the stage of its development, up to the formation of embryos, in the 

 open water. The details with regard to the different species will 

 be found in the following pages. Now according as the ready 

 formed embryo is, or is not, furnished with a boring apparatus, 

 will the mode of its migration vary. The unarmed species are, 



1 I here pass over Verloren's other experiments. The attempt to rear freed embryos 

 in meat or in bread and water always failed. Moreover, I see no reason why any growth 

 should have been expected in this case. At the utmost, if they still exerted an 

 active faculty, they might encyst themselves, when they would not have become more 

 highly developed, but would have been ascxiuil in the manner of the Trichina. A final 

 explanation of this subject can only be obtained by the administration of such eggs to 

 various higher and lower animals. 



