LUCERNARI^ AND THEIR ALLIES. 11;J 



quite small, we judge that they are not of special importance in this region, but 

 rather remnants of an embryonic condition. 



208 (B). The colletocystophoric nmudocustophore in its earlier days has all tlie 

 proportions in shape and numbers of that of a true tentacle of the same age ; and 

 in fact the one could not be distinguished from the other if detached from the 

 body so that their position might not be known. At that period they seem to be 

 of equal value as prehensile organs, but in course of time, as the collctocysts pro- 

 gress in development the nematocysts decrease in number, and the layer in which 

 they are imbedded grows less in thickness. Still as the change is not abrupt but 

 gradual, we should judge from appearances that the nematocystophores retained 

 their power largely until the body had grown to from one-quarter {fujs. 82, 83, 

 84) to one-half its adult size. In the full-grown condition {fi(j. 47), at last, we 

 find a mere remnant (a"), and so faint as to readily escape notice. The nemato- 

 cysts are relatively very few, and the layer of prismatic cells is a meagre repre- 

 sentative of what it once was, a slight knob or undulation on the surface of the 

 semi-transparent area, peculiar to that region of the coUetocystophore. 



209. The opsomyoplax {fig. 47, vx") of the coUetocystophores offers nothing 

 peculiar, or different histologically from what may be observed in the tentacles, 

 but as to the arrangement of the muscular fibrils there is a marked diversity ; yet 

 as that has been given with sufficient details in the general description (^| 105, 

 111) of the layers we will not repeat anything here. 



210. The colletocystophoric chonclromyoplax (fi(j. 47, I/) docs not seem to differ 

 from that in the tentacles {figs. 90, 91, h'), as far as its histoloijical elements are 

 concerned ; not even after it has been so irregularly disposed, as to thickness, as 

 we find it in a fully developed anchor (see ^ 112). The more or less abruptly 

 clianging diversities in the depth of this layer are accompanied by as abrupt short- 

 enings or lengthenings of the fibrils, but not by any other modifications that we 

 could discover. 



211. The gastvophrafjma {figs. 47, i\ 94, 95) of the anchors embodies the most 

 remarkable modifications of cells, excepting the nematocysts and collctocysts, that 

 we have met with in this animal. Yet, as will be seen presently, traces of what 

 liere amounts to a singularity are to be found in other parts of the body, both 

 without and within ; and serve to clear up what appears to be at first glance a 

 strange anomaly. In the depths of the cavity of this organ the gastrophragmic 

 cells are from three to four times deeper than broad ; and on the whole may be 

 set down as prismatic in contour ; each prism occupying the whole depth of the 

 layer {fig. 94, A, B). The wall {d) of each cell is quite thick, especially at the 

 ends, and perfectly transparent and homogeneous in texture ; but it varies in 

 thickness in a most remarkable way, however. This consists in an internal 

 annular thickening of the wall at two points so disposed as to divide the cell into 

 three equal regions. The annular semipartitions are broad at the base, but rapidly 

 run out to a sharp edge, which sometimes projects one-quarter the distance across 

 the cell-cavity, but usually less than this amount. This reminds me of a cell 

 undergoing self-division ; and the disposition of the contents seems to bear out the 

 analogy ; but although rarely, lu-re and there, one of tliese dark internal masses is 



15 Apill, 1878. 



