14 THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. 



area of the manubrium pale green. At the very base of each tentacle there is a speck 

 of shining emerald-green, of the same color as the green portion of the exumbrellar 

 tentacles of Olindioides. These are not eyes. 



The musculature is well developed, but less so than in Olindioides, and the 

 muscular lamellae are confined to the subumbrella. There is, however, a strong mus- 

 cular ring exactly in the same position as in Olindioides, namely, near the base of the 

 velum, just internal to the inner nerve-ring. Here the mesogloea, or, as it may be 

 called, the supporting lamella, is thrown into extensive irregular folds, on either sur- 

 face of which the muscular fibres are closely arranged in a row. 



III. REMARKS ON OLINDIAS MULLERI HAECKEL. 



There are some points in Haeckel's description of this medusa that require com- 

 ment. The following remarks are based on an examination of an excellently pre- 

 served museum specimen of about 50 millimetres in diameter from Naples, that has 

 been in the possession of this school for several years, and of a few examples that 

 have recently been obtained from the Naples Zoological Station, fixed according to 

 my directions. The latter material is, so far as I have examined, in a rather unsatis- 

 factory condition histologically, due, as I believe, to histolysis having set in before 

 fixing. But so far as the general structure is concerned, these specimens can be safely 

 depended on, the more so as there is the perfect specimen as a control. 



The general form of the medusa is very well represented in Haeckel's figure, 

 but the filiform velar tentacles (Fangfaden) are too numerous. In the perfect speci- 

 men above referred to there were only some 35, irregularly distributed along the 

 entire margin, and these are of very unequal length and thickness. There can also 

 be observed various stages in their development from the bulbular to the filiform 

 condition, the bulbular forms being about four or five times as numerous as the fili- 

 form ones. Haeckel (79) also speaks of numerous ocelli situated between the velar 

 tentacles, which, according to him, appear to contain a biconvex lens. These so- 

 called ocelli are nothing but the bases of the exumbrellar or of the filiform velar ten- 

 tacles, which contain a red pigment in the endoderm, and the supposed biconvex 

 lens is simply the axial cavity of the tentacle viewed in optical section. 



The exumbrellar tentacles are armed with incompletely ring-shaped or horse- 

 shoe-shaped nettle-warts, and are provided each with an adhesive patch of mucous 

 cells at the tip. The patch extends on the inner side more than on the outer. The 

 endodermal roots of the tentacles are not very long, but are quite conspicuous. 



