REPORT ON THE HYDROIDA. 



Nematopliores in the Statoplea. 



a. Hijdrocladial nematophores. — These are arranged in two sets on every internode 

 of the hydrocladium, and consist of an azygous or mesial uematophore and a pair of lateral 

 nematopliores. The mesial nematophore is in the form of a tubular process springing 

 from a point of the hydrotheca-bearing internode immediately below the hydrotheca, to 

 the front wall of which it becomes in almost every instance adnate for a greater or less 

 extent of its length. In a very few cases the mesial nematophore of the Statoplean 

 Plumularidse, while fixed immovably by its base, remains free for the rest of its course, 

 having no adhesion to the hytbotheca (PL XVI. figs 1-3). In a single instance [Aglao- 

 phenia hispinosa of the Gulf Stream Eeport^) a second mesial nematophore is developed 

 in a longitudinal line behind the first. 



The mesial nematophore communicates through its base with the cavity of the inter- 

 node, just below the hydrotheca. In that portion of it which is adnate to the front of 

 the hydrotheca it communicates by means of a longitudinal slit-like aperture with the 

 cavity of the latter. It is always open at its distal extremity, where an aperture, usually 

 very oblique, allows of the projection of its protoplasmic contents in the form of free 

 pseudopodia. Besides the terminal and the longitudinal slit-like aperture there is also in 

 many cases an aperture on its inner or hydro thecal side (PL XV.), just beyond the point 

 where its distal portion becomes free from the walls of the hydrotheca. Occasionally an 

 imperfect transverse septum exists in some part of its course (PL XX. figs. 4, 5). 



The mesial nematophore is in a few cases adnate to the walls of the hydrotheca for its 

 entire length. In most cases, however, its distal extremity is continued for some distance 

 as a free pi'ocess. This free distal portion of the mesial nematophore varies much in 

 length. In Aglaoplienia proper it is generally quite short, but in some other genera it 

 attains a great length, being developed in the form of a long curved horn (PL XVIIL). 



The lateral nematophores in the Statoplea are tubular, cup-shaped, or crescentic bodies, 

 always two in number, situated symmetrically one on either side of the hydrotheca, nearly 

 on a level with its orifice or thecostome. They spring from the hydrothecal internode 

 with the cavity of which they communicate by their base. They terminate distally by 



been described by G. 0. Sars {he. cit., p. 112, pi. iv. fig. 10) as developed below the liydrothecEe in his Halecium 

 rjorgonoide. 



Mr. Busk, in a letter which I have recently had from him, describes from a specimen in Ids collection hut from 

 an unknown locality a Hydroid whose affinities are with the Sertularida; rather than with the Plumularidfe, and which 

 yet carries on the front of every hydrotheca a small sessile nematophore-like body. Whether this is to be regarded as 

 a true nematophore or not, can scarcely be asserted with confidence from the examination of a dried specimen. Its 

 peculiar position, lying as it does on the front wall of the hydrotheca, without any apparently direct communication with 

 the hydrocaulus, is certainly against placing it in the same category with the true nematophores. The Hydroid is also 

 very exceptional in other respects, and Mr. Busk regards it as the type of a new genus, for which he proposes the name 

 of Greeneia. 



^ Hydroids of the Gulf Stream, p. 46, pis. xxvii. xxviii. 



