64 MORrHOLOGy OF 



Fig. 93 a. — Longitudinal section of some liver saccules of B. salmoneus 

 One of these is perforated at its end. Obj. A, oc. 2. 



Fig. 94. — Muscle-fibres of B. Robinii (osmic acid preparations). Obj. F, 

 oc. 2. (a) Three isolated radial muscle-fibres from the proboscis cavity. 

 {b) Two adjacent fibres belonging to the longitudinal system of the collar, 

 (c) Two fibres from the same region as (b), which on treatment with osmic 

 acid show an appearance of striping. 



Fig. 95. — Section of the central part of the proboscis gland of B. sal- 

 moneus, anterior to the notochord. Obj. D, oc. 2. 



Fig. 96. — Outer part of the proboscis gland of B. salmoneus, anterior to 

 the notochord, to show the arrangement of the border cells (6r. els.). 

 Obj.CC, oc. 2. 



Fig. 97. — A radial segment of the proboscis gland of B. salmoneus in 

 the region of the notochord. (For the relations of this tissue vide " Later 

 Stages," &c., Figs. 51 and 52.) Obj. D, oc. 2. 



Fig. 98. — Group of cells from the interior of the proboscis sac of B. 

 minutus. Obj. D, oc. 2. 



Fig. 99. — Longitudinal vertical section through the left side of the pro- 

 boscis stalk of B. Kowalevskii (4, ^. «.), to show the internal opening of 

 the tube of the proboscis pore. Obj. D, oc. 2. 



Fig. 100. — Concretions from the living mesoblastic tissues of the 2nd body 

 cavity of B. Robinii. Obj. D, oc. 2. 



Fig. 101. — Transverse section through the collar funnels and first gill-slit 

 of B. Kowalevskii (10,^. .9.). Obj. A, oc. 2. 



Fig. 102. — Transverse section through the collar funnels and upper end of 

 the atrial cavity of B. Kowalevskii (young adult). Obj. B, oc. 2. 



Fig. 103. — Transverse section of B. minutus, passing through the in- 

 ternal opening of one of the collar funnels. (Hypoblastic structures indi- 

 cated roughly.) Obj. A, oc. 2. 



Fig. 104. — Longitudinal iiorizontal section of collar funnel of B. minutus 

 at the level of the opening of the first gill-slit. Obj. D, oc. 2. 



Fig. 105. — Transverse section through middle of collar funnel of B. 

 salmoneus. Obj. B, oc. 2. 



Fig. 106.— Transverse section behind Fig. 105. Obj. A, oc. 2. 



Fig. 107. — Transverse section through external opening of the collar funnel 

 of B. salmoneus. Obj. A, oc. 2. 



Fig. 108. — Half diagrammatic transverse section of generative region of 

 male B. Kowalevskii. 



Fig. 109. — (a) Spermatoblast cells, forming the outer zone of the testicular 

 follicle. (A) Spermatoblast cells, forming the inner zone of the testicular 

 follicle, (c) Spermatozoa in the interior of the follicle. Obj. F, oc, 2. 



