152 E. W. MACBETDE. 



age space due to action of preserving fluids on great interradial muscle. //. r. 

 Pedicle of ovoid gland ( = Kohler's hfemal ring ?). 



Fig. 2 b. — Another section of ovoid gland from tlie same series, st. c- 

 Proximal parts of stone canal. 



Fig. 2 c. — Horizontal section of ovoid gland of another adult, sinus b. 

 Transverse section of the canal sinus. 



Fig. 2d. — Nuclei suggesting direct division from another adult organ. 



Fig. 2e. — Diagram of relation of gland and surrounding sinuses in the 

 adult. »2.jo. Madreporic pore. 



Fig. 3. — From an individual about '2 mm. in diameter, msch. Mesenchyme 

 filling ventral portion of the ccelom. 



Figs. 4 a, b, c. — Three consecutive sections from a somewhat older individual 

 than Fig. 3. m. p. Madreporic pore. ov. g. First rudiment of the ovoid 

 gland. 



Figs. 5 a, b. — Two sections from a series through an individual about '25 

 mm. in diameter, gen. r. First appearance of primitive germ-cells, simis b. 

 A nook of the ccelom, afterwards becoming the axial sinus. 



Figs. 6a, b, c. — Three sections from a series through an individual "3 mm. 

 in diameter, sinus b. Axial sinus slill communicating with coelom though its 

 lumen is obliterated, simis a. A nook of the ccelom, afterwards becoming 

 aboral sinus. 



Fig. 6d. — Diagram of relations of the rudiments of axial and aboral 

 sinuses to each other and to the incipient ovoid gland. 



Figs. 7 a, b, c. — Three sections from a series through an individual "4.8 mm. 

 in diameter, gen. r. Solid knob in which incipient aboral sinus and genital 

 rachis end. h. r. Prolongation of the ovoid gland over the dorsal surface of 

 the nerve-ring. 



Fig. 8.— Section of an individual '83 mm. in diameter. Osmic alone. 

 sinus a, sinus b. Sharply separated axial and aboral sinuses. 



Figs. 9a, b. — Two sections from a series through an individual "58 mm. 

 in diameter, gen. r. Genital rachis constricted off from ovoid gland. 



Fig. 10. — Oblique section of an individual "59 mm. in diameter. 



Fig. 11. — Section of an individual "9 mm. in diameter, x. Curious branched 

 cell in the axial sinus. 



Fig. 12. — Another section from same series as Fig. 11, showing growing 

 branch of rachis. t. Position in which testis will be formed. 



Fig. 13. — Young testis from an individual about -97 mm. in diameter. 



Fig. 14. — More advanced stage of testis. From an individual '9 mm. in 

 diameter. 



Fig. 15.— Adult testis. 



