r^y LUCEKNARIvE AND THEIR ALLIES. 



arc very slender and extend far out of the mouth of the proboscis, and at another, 

 l\wy are sliort(>ned down to broad, ovate bodies with blunt tips, and more than 

 usually convex sides, approxinuxting to fusiform. As to flexibility they seem to be 

 unlimited, and so in regard to plasticity ; now coiling like a mass of suckers, in an 

 apparently indissoluble tangle, or spreading laterally, and folding at the sides, 

 assuming a deeply concavo-convex sliape, as if a sac with a wide lateral aperture. 

 In the latter condition they have a wonderful resemblance to the laterally opening 

 genital sacs. We have illustrated the two, side by side, at the time when the 

 di(/ltuU were in the sacciform attitude (fi'j. 80, >?, «')• It would be difficult to state 

 precisely what their size is, still there is probably a limit to it. When tliey elongate 

 they also become more slender, and when they shorten they also widen, at a 

 corresponding rate. An average length is about equal to the greatest breadth of a 

 triangular genital half, or half as long as a fully extended tentacle. 



117. Fiuicf ion.— The flattened lanceolate form of these bodies is by no means 

 independent of other characteristics, of which there are two principal ones. In the 

 first place the broad faces are turned respectively toward and away from the pro- 

 boscis, and in the second place, that face tvhich looks toward the proboscis is covered, 

 except near the tip, with a dense lai/er of coUetocysts {Jig. 98, A), while the opposite 

 face and the excepted part of the other side, are beset vnth nematocysts, and heavily 

 clothed with vihratile cilia (B, C). Between these two sets of organs there is a 

 sharp line of demarcation, and evidently, from the nature of their constituents, 

 devoted to quite diverse- functions. The proximity of these bodies to the proboscis 

 and their occasional protrusion from the mouth, conjoined witli the presence of 

 colletocysts and nematocysts, all tend to indicate their use as prehensile organs, 

 either in the transfer of food inwardly, or in the removal of material, fecal matter, 

 or perhaps eggs, from within outward. Their adhesive powers are great, and their 

 urticating organs are numerous, and no doubt serve more efficiently than the 

 tentacles to reduce the struggles of prey, shrimps and otlier animals, and bring 

 them into manageable condition for being thrust into the lateral camerae of the 

 unibella. 



118. The Gastrophragina. — The walls of the digituli are direct prolongations from 

 the three innermost strata of the anterior umbellar parietes. The gastrophragma 

 is doubled in thickness as it becomes the peripheral layers {fgs. 98, 99, 100, i^) 

 of these bodies. Its imier as well as exterior outline is sharply defined, particularly 

 on the side (A) facing toward tlie proboscis, because it is there composed almost 

 entirely of colletocysts («), witli their dense, semi-opaque, granular contents. 

 Toward tlie tip (C) its inner surface is rather irregular and somewhat thicker than 

 elsewhere. 



119. The muscidar layer {li) is tlie only division of the gastromyoplax (or 

 odmyoplax) which is not exclusively devoted to the genital saccules. It is very 

 tliin, almost filmy, scarcely measuring one-sixth the depth of the gastrophragma, 

 and then only where it is tliickened into ridges. The latter appear, with a low 

 power, to be coarse longitudinal stria?, but a closer examination, with a higher 

 amplification, proves them to be interrupted ridges {fig. 99, h), trending parallel- 

 wise to the longitudinal axis of the digitidus, abng 'the exterior surface of the 



