Chap. I. 



REPRODUCTION" OF CORYNE MIRABILIS. 



199 



Fig. 18. 



Fig. 19. 



Sectional view of a ra- 

 diating tube (c), and tlie 

 ndjoiiiintj middle (6) and 

 innermost {</) walls. 



Vertical section of the edge of 

 the bell. 

 aa' outer wall.— 66' middle wall.— 



c c' innermost wall. — d circula'' 



tube. 



The three component walls of the disk are excessively thin, making it very diffi- 

 cult, even with a magnifying power of five hundred diameters, to recognize any 

 thing more than a thick, dark line, as the representative of the thickness of each 

 (PI. XIX. Figs. 16, ^' h-' o\ and 11, a c, wood-cuts \^, h d, and 1% a b c, a' b' c'). 

 For a short distance before the middle 

 (PL XIX. Mffs. 15, h', and 16, h^) and inner- 

 most walls (f) join the proboscis, they 

 become more easily discernible, from an 

 increase in thickness, which reaches its 

 maximum (y k) in the organ just men- 

 tioned. The middle wall is quite thick 

 where it becomes an integral part of the 

 radiating tubes (PI. XIX. Figs. 16, e, and 

 17, b, wood-cut 18 c). Just before the medusa frees itself, 

 and whilst confined within the close embrace of the horny 

 film (PI. XIX. Fig. 11, c), the unexpanded outer (a), middle (b), and innermost walls 

 (c), exhibit considerable thicknes.s, allowing the component cells («' c') of the outer and 

 inner ones to be recognized ; but the moment these walls are liberated from restraint, 

 they take on the conditions described above. The innermost wall is perfectly free 

 from. the middle wall, except at the radiating tubes and the four intermediate points. 

 This becomes apparent when the disk is contracted, at the time the animal is 

 dying. Then this wall shrinks from the middle one, between the points of attach- 

 ment, and, according to the degree of contraction, forms a figure with eight ano-les, 

 more or less sharply defined (PI. XVIII. Figs. 16, a, 17, e, and 18). The bulbous 

 swelling (PI. XVIII. Figs. 15- and 17; PI. XIX Figs. 17, a\ and 18, c) on the under 

 side, at the base of the tentacles, and the eyes (PI. XIX. Figs. 17, d, 18, a, and 

 19, «), are, proportionally, from three to four times as large as in the full-grown 

 medusa. When seen in profile, either from above or laterally, it becomes evident 

 that the eyes occupy the whole thickness of the outer wall of the tentacle, and 

 that they have a truncated, conical shape, with the narrower end turned inwards 

 (PI. XIX. Figs. 17, r7, and 19, a). 



As to a nervous system, it has not been possible to detect the least signs of 

 a structure indicating its presence. When the innermost wall (PI. XIX. Figs. 16, 

 g\ and 17, c) is seen in profile, along the radiating tubes and at the four inter- 

 mediate points, its thickness resembles a thin cord, which might be easily mistaken 

 for a nervous thread. The most intimate structure, the cells (PL XIX. Fig. 13, i). 

 of the innermost wall, along the radiating tubes, do not differ from those on each 

 side [a); all are alike excessively transparent, and round. When the animal is 

 contracted in the manner described above, the innermost wall, at its eight points 



