Way? Ine ” 
REPORT ON THE HYDROIDA. 15 
was present on the second internode, which was here larger than the others, and carried 
a mesial as well as a pair of lateral nematophores; while the continuation of the rachis 
was arched over the gonangium, and had the persistent lateral nematophores of each 
internode curved backwards so as to be directed towards the convex side of the arch. It 
would seem to be only on the second internode that a gonangium is borne, and here it 
takes the place of the hydrotheca, which, had it not been suppressed, would have 
belonged to this internode, while the mesial and lateral nematophores are retained. 
In Lytocarpus saccarius, a species from Ceylon,’ the gonangia are borne near the 
distal extremity of short ramuli, which are hydrocladia in which the transformation has 
been less complete than in the cases described above. In the specimens examined these 
ramuli were composed each of three internodes. The proximal two internodes carried 
hydrothece in all respects like the other hydrothece of the colony, but im the distal 
internode the hydrotheca was suppressed, while its mesial and lateral nematophores 
remained with but little modification, and the solitary gonangium occupied the place of 
the suppressed hydrotheca. 
In Lytocarpus secundus (Pl. XIV.) certain hydrocladia undergo a remarkable modifi- 
cation in order to become converted into phylactocarps. Their internodes, which are 
reduced to seven or eight in number, lose their hydrothecz entirely, and carry each a 
long curved spine-like appendage, which is supported on the end of a short process of the 
internode, and bears a double row of eup-like nematophores, several nematophores of a 
similar form being sessile on the internode itself (fig. 5). 
Though no gonangia were developed in the specimens examined, it will scarcely 
admit of doubt that the hydrocladia thus modified are true phylactocarps. Analogy 
would, perhaps, justify us in regarding the spine-like appendages as the mesial nemato- 
phores of the suppressed hydrothecee, while the lateral nematophores have left no 
representatives. A comparison of these appendages with the cost of a true corbula at 
once suggests itself, nothwithstanding their disposition in a continuous series along the 
mesial line of the rachis, instead of being thrown alternately to the right and left. In the 
absence of gonangia, however, the exact relations of the parts of the phylactocarp to the 
gonangia, which may yet become developed on it, cannot be ascertained with certainty. 
In the only known forms of Eleutheroplea in which phylactocarps have been detected 
these structures appear to be in all essential points modified hydrocladia, a number of 
which combine to form the phylactocarp. In Hippurella annulata, as described by Fewkes, 
the hydrocladia lose their hydrothece, and assume a verticillate disposition, arching over 
the gonangia, which are borne by the stem near their bases. In Callicarpa gracilis, 
Fewkes, the hydrocladia undergo a similar modification, and, moreover, become dichotom- 
ously branched.’ This dichotomous division of a hydrocladium is not without analogy, 
1 Linn. Soc. Jowrn. Zool., vol. xii. p. 277, pl. xxii. The species is there referred to the genus Halicornaria, 
2 Bull, Mus, Comp. Zool., loc. cit., p. 134, pls. i., ii. 
