100 JOURNAL OF THE 



of as eggs are probably fat globules. I have found potatoes 

 here affected with a similar disease while also attacked by 

 Heterodera radiclcola. I hav^e found the worms representing all 

 stages of development. It appears that they do not form cysts 

 in the proper sense of the word. Fig. 46, Plate VI, represents 

 a mature female of this worm. At a is a fully developed egg 

 yet within the uterus, while b represents young ova not fully 

 developed. In the body of the worm, as well as in the eggs, 

 can be seen the round globules. Figs. 42 and 43 represent eggs; 

 43, an egg having undergone fission. Other eggs were observed 

 in different stages of development up to the fully formed larva 

 represented still within the tgg membrane at Fig. 44. Fig. 45 

 represents young worms of this species. 



Fig. 47 represents a different species occasionally found accom- 

 panying these worms, but whether they are parasitic or not I 

 have not yet had the time to determine. 



Several of the worms which Dr. Neal has fio-ured do not 

 belong to Heterodera. Especially in decaying tissues one is apt 

 to find species which are not parasitic. However, wherever they 

 were found it is very clear that some belong to other genera than 

 the worm in question. For example, his Fig. 2, Plate XIII 

 (loG. cit), is a mature female of another genus. An egg is rep- 

 resented in the uterus near the letter B, and the numerous yolk 

 globules he speaks of as a peculiar arrangement of cells. 



Comparison with Heterodera Schaohtii, Schmidt. — 



There are many points of very close resemblance between 

 Heterodera radicicola and Heterodera Schachtii. Both of these 

 are European species, and each is known to attack widely differ- 

 ent plants, so that the selection of a particular plant or family 

 of plants as a specific peculiarity is not their habit. Notwith- 

 standiiig the points of resemblance there are a number of differ- 

 entiating characters heretofi)re used, the value of which can only 

 be determined after careful study and experimentation, and even 

 now some of these are known to be variants possessed by both 

 species. The female of Heterodera Schachtii is said to be ecto- 

 parasitic, the posterior part of its body being nearly or quite 



