489] LARVAL TREMATODES—CORT 43 



crura could be traced smaller vessels leading from the posterior end of 

 the body, and forming a loop at the region of the pharynx similar to 

 that of the echinostomes. 



The nervous system shows very prominently both in living and 

 preserved specimens and its larger branches can easily be traced. It 

 shows nothing peculiar. From the large masses on each side of the 

 prepharynx two branches pass out to the oral sucker. Laterally there 

 are two branches on each side in the pharyngeal region, and strands 

 can be traced almost to the posterior end of the body. 



That the specimens of Cercaria reflexae which came under my ob- 

 servation were well along in development is attested by the condition of 

 the reproductive anlage (Fig. 43). It is divided into four definite 

 areas. In the region of the mid-line just in front of the excretory 

 bladder are three masses of nuclei, one in front of the other and close 

 together. The posterior two which are smaller than the other probably 

 represent the anlage of the testes, while the anterior larger mass of 

 nuclei the anlage of the ovary and the structures surrounding it. Just 

 in front of the acetabulum is a mass of nuclei representing the future 

 ends of the reproductive ducts. The course of the ducts connecting 

 these areas could not be traced. 



The rediae of Cercaria reflexae (Fig. 45) were present in different 

 stages of development in the infected snails, altho there was a great 

 preponderance of the fully matured forms. The smaller rediae were 

 very active in extending and contracting their bodies, and were able 

 to make progress with the aid of their posterior locomotor appendages. 

 The largest forms were sluggish and reduced to mere sacs containing 

 cercariae. 



The smallest rediae have much the same structure as those of 

 Cercaria trivolvis. One of them measured 0.28 mm. in length and 0.054 

 mm. in width and had the posterior locomotor appendages 0.22 mm. 

 from the anterior end. The anterior ridge or collar was very promi- 

 nent, 0.022 mm. from the anterior end, and the pharynx had a diameter 

 of 0.043 mm. A number of small germ balls were present in the body 

 cavity and the intestine extended to the region of the posterior locomotor 

 appendages. 



A redia somewhat larger than the one just described is shown in 

 figure 44. In this form the cercariae are beginning to be developed into 

 recognizable form. 



The nervous system was quite well developed in the young rediae 

 of this species. In one very immature specimen studied while alive 

 two large nervous masses (Fig. 46, n) could be distinguished on each 

 side of the posterior part of the oral sucker, which sent two branches 



