REPORT ON THE HYDROIDA. 



Nematophores in the Eleutlieroplea. 



The uematopliores here belong, iu almost every instance, exclusively to the moveable 

 type. In very rare cases (PI. VIII. figs. 1-3) the moveable nematophore is associated 

 with a fixed nematophore developed in other parts of the same colony. 



a. Hi/drodadial nematophores.— T\\fi hydrocladial nematophores in the Eleutheroplea 

 are, as in the Statoplea, disposed in two sets — mesial and lateral. The mesial nemato- 

 phore is never, as in the Statoplea, adnate to the front of the hydrotheca, and is almost 

 always removed to a point at some distance from the hydrotheca at its proximal side. 

 It is this azygous nematophore which in very rare cases differs from the others in being 

 immovable. In one instance, that of Schizotricha muUifurcata (PI. VII. figs. 4, 5), 

 the single mesial nematophore is replaced by a pair of nematophores, one on each side of 

 the internode. In some cases an azygous nematophore is also found on the hydrothecal 

 internode at the distal side of the hydrotheca, whUe in Plumularia armata (PI. IV. figs. 

 3, 4) this part of the internode supports, instead of a single mesial nematophore, a pair- of 

 lateral nematophores. 



In every case the hydrotheca^ of the Eleutheroplea are flanked, as in the Statoplea, by 

 a pair of lateral nematophores.^ Each of these is usually borne on the summit of a hollow 

 chitinous process, which springs from the internode at either side of the hydi'otheca. 

 The process varies much in length, and is sometimes obsolete. 



The hydrocladia of the Eleutheroplea difi'er from those of the Statoplea in being very 

 often provided with iuternodes which do not carry hydrothecae (PI. I. figs. 1-4). The 

 internodes thus destitute of hydrothecse carry nematophores which are either solitary or 

 are disposed in a longitudinal series on the front of the internode. 



b. Cauhne nematopliores. — These are borne, generally in considerable numbers, along 

 the stem and branches, and are often disposed in pairs close to the points from which the 

 ultimate ramuli or hydrocladia spring (PI. V.). 



c. Gonosomal nematophores. — When these are present in the gymnocarpal Eleuthero- 

 plea they spring from the gonangium, where they are usually disposed in a symmetrical 

 pair on its proximal end, and are here in connection with the base of the blastostyle 

 (PI. IV. figs. 2, 6). In some cases they are connected with other parts of the blastostyle, 

 which is then pushed out of the axis of the gonangium, and lies in contact with its wall 

 (PI. IV. fig. 4). In such cases the wall of the gonangium is perforated along the course 

 of the blastostyle, and the contents of the nematophores, which are developed externally, 

 communicate through the perforations with the blastostyle. 



In another very remarkable form {Sciurella indivisa, PL V.) the blastostyle is 

 extensively ramified, and the ends of the ramification impinge on definite points sym- 



1 Iu the rare cases in which these lateral nematophores are stated to he absent, I believe that they have either been 

 overlooked in consequence of their minuteness, or have fallen away from their points of attachment. 



(ZOOL. CHALL. EXP. — PART XX. — 1883.) U 2 



