Chap. I. 



REPRODUCTION OF CORYNE MIRABILIS. 



195 



unless carefully 



of its component laj^ers (wood-cut 13). The outer wall (b), embracing the whole 

 medusa-bud, bends upon itself {/j% at the edge («^) of the cup of the inner Avail 

 (a), and, following the inner surface of the latter, there be- 

 coming the innermost of the three walls of which the um- 

 brella is composed in the newly freed medusa, passes to and 

 over the proboscis («>), where it constitutes the outer wall. 

 In this way, the cup-like disk of the medusa becomes triple- 

 walled {l> a /?), and the proboscis double-walled {n ii^). If 

 we include the radiating tubes in a section, the inner wall 

 being doubled by having a channel hollowed in its thick- 

 ness, then the disk appears quadruple-walled (PI. XVIII. 

 Fiff. 9, b a a^ c), and may be mistaken as having really four walls, 

 examined in all its relations. , 



Other parts of the organism have also developed new features; the radiating 

 tubes have broadened considerably, especially at two points (PI. XVIII. Fi(/. 9, /) 



of each, half way between the base and extremity, so that 

 the channels of neighboring tubes are diverted laterally into 

 broad sinuses. Of course this will be understood to be a 

 hollowing in the thickness of the middle wall. As the me- 

 dusa grows larger and older, these sinuses become narrower 

 and deeper (PI. XVIII. F/ff. 10, and wood-cut 14, I), and con- 

 sequently each one approaches its neighbor. What appear 

 to be intervening walls, both in the last stage (PI. XVIII. 

 F/(/s. 9, i' I c) and in this {FI(/. 10 and wood-cut 14, // I c), 

 through which the approximating sinuses would appear to 

 be forcing their way, are profiles of an oblique view of the 

 innermost wall, seen at a deeper focus.^ That portion beyond the approximating 

 sinuses, and the outer end of the disk (PL XVIII. Fi(/. 10, and wood-cut 14, b^), is 

 deeply four-lobed on the inner surface, each lobe (b^) being separated from its 

 neighbor by a deep sinus (b^). This sinus extends so far, outwardly, that the edge 

 of the disk is reduced to a quite thin stratum (b-). These four lobes are the 

 incipient hollow tentacles, which, as they grow older and longer, are gradually bent 

 inward, as may be seen PL XVIII. F/'ff. 14, and wood-cut 17, /. 



In a little older stage, we find that the lateral sinuses, of the last phase, have 

 come together and formed a continuous channel (PL XVIII. Fit/. 11, and wood-cut 



' In order to avoid confusion, only two of the 

 radiating tubes, nearest to tlie eye, are sliown in 

 Figs. 9 and 10. Being very broad, those portions 



of the tubes which are next the centre of the 

 figure, are seen facing the observer, and those at 

 the periphery nearly in perfect profile. 



