3o6 DISCOVERY REPORTS 



openings, or, more precisely, it is an intricate mass of trabecular cuticular matter which leaves but 

 little space between the bars and lamellae composing this cuticular mass. In Fig. 16 b the connexion 

 of the internal part of the organ of fixation with the root system through the sieve plate is more apparent 

 than in Fig. 16a. 



Undoubtedly young specimens of A. capillosiis possess a sieve plate through which protoplasmatic 

 excrescences from the internal part of the organ of fixation penetrate into the tissues of the host. 



Fig. 15. Same specimen as Figs. 12-14, transverse section of the rostral region slightly behind the base of the free rostrum. 

 Letters as in Fig. 12. In addition: t, trophomere. x 67. 



During further development the increasing volume of the external part of the parasite causes a need 

 for a stronger fixation of the internal parts. As the functioning root system then has penetrated for 

 a comparatively long distance into the organs of the host, the proximal part of the root system then can 

 be added to the organ of fixation by the formation of additional cuticular matter. The sieve plate, 

 which in young stages must have formed an important part of the parasite, during growth of the 

 organism gradually must have lost its original function. Though in older stages it is no more of special 

 use to the parasite, the sieve plate has remained where at first it was formed. 



Fage (1938) describes the lower surface of the organ of fixation of A. copillosus as having a rough 

 surface. In the figure (loc. cit., fig. 3) this is also indicated. Undoubtedly the specimens examined by 

 Fage had the same structure of the internal parts as the specimen described above. The rough 



