ZYGODACTYLA. 



59 



numerous, the whole inner surface of the disk being ribbed with 

 them. (See Figs. 74 and 75.) The ovaries follow the length of 

 the tubes, though they do not extend quite to their extremity, 

 where they join the circular tube around the margin of the disk ; 

 nor do they start exactly at the point where the tubes diverge 

 from the central cavity, but a little below it. (Fig. 74.) Each 

 ovary consists of a long, brownish, flat bag, split along the mid- 

 dle, so closely folded together that it seems like a flat blade 

 attached along the length of the tube. Perhaps a better compar- 

 ison would be to a pea-pod greatly elongated, with the edges split 

 along their line of juncture, and attached to a tube of the same 

 length. The ovaries are not perfectly straight, but slightly wav- 

 ing, as may be seen in Fig. 74, and these undulations are stronger 

 when the ovaries are crowded with eggs, as is the case at the 

 time of spawning. 



The large digestive cavity hangs from the centre of the under 

 side of the disk (Fig. 75), terminating in the proboscis, which, in 



Fig. 75. 



this kind of Jelly-fish, is short in proportion to the diameter of 

 the disk, while the opening of the mouth is very large. (Fig. 74.) 

 It is unfortunate that a variety of inappropriate names, likely to 

 mislead rather than aid the unscientific observer, have been ap- 

 plied to different parts of the Jelly-fish. What we call here di- 

 gestive cavity, proboscis, and mouth, are, in fact, parts of one 

 organ. An exceedingly delicate, transparent, filmy membrane 

 hangs from the under side of the disk ; that membrane forms the 

 outer wall of the digestive cavity, which it encloses ; it narrows 



Fig. 75. Zygodactyla seen in profile. 



