TUBULARIA INDIVISA. 207 



tentacles of a specimen which hnd been long preserved in spirits. Two sets of striae, a longitu- 

 dinal and a transverse were visible in the interval between ectoderm and endoderra. Of these 

 the longitudinal striae were the more distinct and were manifestly the expression of longitudinal 

 fibrillac. On tearing the tentacle these fihrillae might sometimes be isolated, when they were 

 seen to be tubular, with a diameter of ai)out ;,;,,3 of an inch. They are perfectly smooth, but in 

 many cases a very distinct oval nucleus, having a shorter diameter of about ^„^ "f a" inch and 

 with a brilliant nucleohis, was visible in them. They might occasionally be seen to taper away 

 to a point, and I have little doubt of their being greatly elongated fusiform cells (fig. G). 

 The transverse strias may also re[)resent a fibrillated layer, but I am by no means so certain of 

 this, and yet I can scarcely regard them as rugae resulting from the contraction of the tentacle. 



In longitudinal section (PI. XXIII, fig. 1) the hydranth is seen to contain a capacious cavity. 

 A little within the mouth the endoderm is thrown into prominent patches of a bright carmine 

 colour, with intervening paler furrows. Passing downwards from the mouth the carmine-coloured 

 patches are replaced by smaller spots ; still further down these become resolved into minute 

 puncta, which at the base of the hydranth-cavity are arranged in radiating striae. 



A little above the origin of the posterior tentacles the endoderm sends off a zone of 

 pendulous fusiform lobes (PI. XXIII, fig. 1, c, and figs. 2 and 3). These lobes are composed of 

 large cells containing carmine-coloured granules, among which may be seen several clear spherules, 

 apparently oil-drops (fig. 3). 



T/ie Gonophores. — The gonophores form pendulous raceme-like clusters, which spring from 

 the body of the hydranth immediately within the proximal zone of tentacles (PI. XX, figs. 2 and 

 3). They are adelocodonic, and are in the form of oval sacs borne on the summits of short 

 peduncles, which are given oft' alternately from a common tubular stalk whose cavity directly 

 communicates with that of the hydranth. In each raceme the gonophores increase in maturity 

 as they recede from the base of the common peduncle. The racemes thus differ from the inflor- 

 escence, which the botanist designates by this term, in being centrifugal instead of centripetal in 

 their evolution (see above, p. lOS). 



In the walls of the gono[)hores three layers may be distinguished — an external (ectotheca, 

 PI. XXIII, figs. 8 and 11, d), a middle (mesotheca, b), and an internal (endotheca, e). The 

 ectotheca is perforated by an aperture in a point which is more or less diametrically opposite to 

 the point of attachment of the peduncle ; abundance of thread-cells are ind^edded in it. The 

 mesotheca is rendered obvious by the presence in it of four radiating canals (c), which extend from 

 the proximal towards the distal end of the gonophore, where they become united by short trans- 

 verse branches, forming a circular canal, which surrounds an aperture [d) in the mesotheca exactly 

 corresponding to that of the ectotheca ; where the radiating canals enter the circular canal they 

 become dilated into small bulb-like expansions, containing accumulations of coloured granules. 

 The endotheca in the female gonophore (fig. 11) disappears at an early period, apparently under 

 the pressure of the increasing mass of the generative plasma which is formed within it, though 

 it continues longer as a distinct membrane in the male (fig. 8) . 



Occupying the axis of the gonophore is the large club-shaped spadix surrounded by the 

 generative mass (/). It consists of a hollow process of endoderm, whose lining cells are filled 

 with carmine-coloured granules and have their free surfaces clothed with vibratile cilia (fig. 10). 

 The radiating canals spring from the base of the spadix, where they comnmnicate with its cavity. 



The spadix in a very early stage is invested by a layer of ectoderm, but the generative 



