212 VOGTIA SPINOSA. 



facets, as yet hardly divided by the dorsal angle (Plate 15, fig. 11). In a slightly 

 older example (Plate 15, fig. 12), the dorsal angle is so much more prominent, 

 that the form is now clearly pentagonal. 



All the specimens were examined to test the constancy of the occurrence 

 and arrangement of spines, and in all but one they showed the typical condition 

 outlined above, though with some minor individual variation in the number and 

 precise location of the spines, a variation which might have been expected. In 

 a single example, however, while the youngest nectophores wore spinous on their 

 dorsal and dorsolateral facets, the oldest three have no spines on either angles or 

 facets, although they are of the usual pentagonal form. The colony is in such 

 good condition as a whole that the absence of spines can not be charged to poor 

 preservation. So constant in occurrence and location are these structures in all 

 the other specimens and so typical are they in the young nectophores of the 

 aberrant example, that their absence in the older nectophores is difficult to 

 account for. But a sporadic variation of this kind does not point to a connec- 

 tion between the "spinosa" and " pentacantha" types of spination. On the 

 contrary, in this specimen there is an entire abortion of spines which are well 

 developed at a younger stage, whereas in V. pentacantha (Bigelow, : lib, p. 351) 

 there are no spines on the facets at any stage in growth. 



The nectosac is broad and shallow as in Hippopodius, and its four radial 

 canals (Plate 15, fig. 9-12) follow a nearly direct course, as in that genus. 

 Haeckel ('88b) has already observed that there is a crescent-shaped ventral sinus 

 connected with the ventral radial canal. In young nectophores this sinus, walled 

 with flat tile-shaped cells, covers nearly the entire upper surface of the nectosac 

 (Plate 15, fig. 11), but with the increasing development of the nectophore, it 

 becomes proportionately much smaller. The pedicular canal, of course, con- 

 nects with the axial canal of the "Knospungszone." 



Stem and appendages. In life the stem was extensible to a considerable 

 length. The individual appendages so closely resemble those of Hippopodius 

 that no extended account is necessary here. I may, however, call attention 

 to the fact that, as Kolliker observed for V. pentacantha, each cormidium has 

 both d' and 9 gonophores (Plate 15, fig. 8). The tentilla (Plate 15, figs. 6, 7) 

 very closely resemble those of Hippopodius. In V. pentacantha, according to 

 Kolliker ('53), Keferstein and Ehlers ('61), and Claus ('63), the tentilla are bright 

 yellow, but in the present specimens they were brick-red in life. Should this 

 color difference prove constant it might be considered a specific character. But 

 color among Siphonophores is so often variable that it is unsafe to lay stress 

 upon it until it has been tested. 



