ELTSHA MITCHELL SCIENTIFIC SOCIETY. 99 



scolex, or in some case^ the brood capsules, from which several 

 heads are produced. In Heterodera tlie vesicular distension of 

 the larva begins after a period of wandering through the tissues 

 of its host. Instead of invagination the wall of the male vesicle 

 is cast, and retains the cystic form while the worm eL)ngates and 

 coils within it. In its ''pupa" condition the male more nearly 

 resembles Eclduorhynchus, where the embryo after a wandering 

 state comes to rest in the tissue of its host, develops a small elon- 

 gated larva, which is surrounded by its firm external skin as a 

 cyst.* The female vesicle continues to distend until in age its 

 body is filled with eggs and young larvse. This condition of 

 the female has been termed by somef a " brood capsule," but it 

 of course bears no morphological semblance to the brood capsules 

 of certain Cestoda. I regret that I find it necessary here to call 

 attention to some serious errors on the part of some of our 

 American investigators. 



One of these errors is that into which Dr. NealJ has fallen in 

 his treatment of the life history of this parasite. He speaks of 

 the eirgs as "cvst^." This mav have been due to the fact that 

 he regarded the numerous yolk globules in the ovaries as cells, 

 for he speaks of the cysts [loc. cit.) which were at first without 

 any "epidermis," being formed by "an agglomeration of cells.^^ 

 What he represents in Plates IX and X, as segmentation of the 

 "cysts," is only a representation of the first stages of segmenta- 

 tion of the egg. 



It appears that Professor Scribner made a similar mistake in 

 speaking of the "cysts" and "eggs" of the nematode which 

 causes the new disease of the Irish§ potato described by him. 

 What he speaks of as the "cysts" are the egg membranes still 

 containing the young larv?e. What he figures as the mature 

 worm is a young one, and the round granules which he speaks 



*Text-book of Zoology, Clans and Sedgwick, Vol. I, p. 382. 



fStrubell, Ad. Untersnchungen uber den Ban nnd die Entwickelung des Rubennema- 



toden, Heterodera Schachtii Schmidt. Bibliotheca Zoologiea, Heft 2, 1888. 



Centralblatt fur Bakteriologie und Parasitenknnde. Band VJ, No. 15, pp. 423-429, Jena, 

 1889. 



IBulletin 20, U. S. Dept. of Agr., Division of Entomology, Washington, 1889. 



gBulletin of the Agr. Exp. Station, Tenn, Vol. II, No. 2, 1889. 



