278 H. J. VAN CLEAVE 



near the genital orifice each Hgament contains a single large 

 star-shaped nucleus. 



Eorhynchus longirostris. In this form the vagina, from the 

 genital orifice to the sphincter, is supplied with four nuclei, as 

 shown in figure 27. The two nuclei associated with the sphincter, 

 which can be made out clearly in serial sections, are not shown in 

 this drawing. Anterior to the sphincter are four vaginal nuclei. 

 The uterus, as in all other species studied, has but two nuclei 

 and these occur at its posterior extremity. As & consequence of 

 the difficulties involved in studying the selective apparatus, as 

 pointed out above, the writer has been unable to estabhsh any 

 definite results regarding the occurence of nuclei in that organ. 



Eorhynchus emydis. In immature individuals of this species 

 the female tract presents a very diagrammatic arrangement of 

 the component structures. Figure 40 shows the nuclei with which 

 the vagina below the sphincter is supplied. These four nuclei 

 are arranged in pairs, one at either end of the region. The sphinc- 

 ter muscle has a single pair of nuclei. Anterior to the sphincter 

 the thick walled portion of the vagina has four nuclei arranged 

 in two pairs as shown for Eo. gracilisentis. The uterus has a single 

 pair of nuclei at its posterior extremity. In the selective appara- 

 tus six pairs of nuclei could be seen distinctly. Of the two mus- 

 cles (fig. 40, ssa) for the support of this organ each bears a single 

 nucleus. 



Eorhynchus tenellus. Reference to the" figure will show that 

 the female genital tract of this species (fig. 39) bears identically 

 the same nuclei as have been described for Eo. emydis. 



11. The brain 



Eorhynchus gracilisentis. In the brain of Eorhynchus condi- 

 tions are such as to render a careful analysis of the structure dif- 

 ficult. This organ (fig. 8, hr.) is a conical mass of ganglion cells 

 having an extreme length of 0.1 mm. The cells of which this 

 mass is composed are small rounded bodies of uniform character 

 so that there are no regions demarcated by variations in the size 

 or structure of the component cells. The small, 0.005 mm., cells 



