'3i 



lower part of the left hand branch in fig. 4; and thus appear as isolated, nearly vertical units 

 which lie in the middle of the branch. In the older parts of the colonies each "series" may 

 be reduced to a single zooecium, as shown in the proximal part of fig. 1 ; the normal disposition 

 being attained in younger parts of the same branch. Minute calcareous teeth commonly 

 project into the peristomes. 



One of the most characteristic features of the 'Siboga' specimens is the presence of 

 cross-connexions between the branches, as shown in figs 4 and 5. These vary greatly in their 

 degree of development, even in different parts of the same colony. Thus in specimen 99. A., 

 from which the figures just referred to are taken, the following conditions were observed: 



(I) A tube (kenozooecium) which has all the relations of the outermost zooecium of its 

 series grows across to the next branch, with some part of which it unites firmly, leaving a 

 suture between itself and the branch with which it has united (figs 4, 5). The kenozooecium 

 develops no orifice; 



(II) the connexions may be widely separated from one another, giving rise to elongated 

 meshes, or tvvo may develop close together; sometimes, as in fig. 5, one from each of the 

 participating branches ; 



(III) the connexion may be two zooecia wide, and orifices may develop on the zooecia 

 which take part in its formation (fig. 4, middle of figure) ; 



(IV) a stouter connexion may be formed, by a bundle of several kenozooecia which 

 develop no orifices ; 



(V) if the next branch does not lie in a suitable position the connexion may run across 

 it, without meeting it, and may unite with the branch next but one to that from which it has 

 taken origin. 



In addition to these formations a considerable proportion of the specimens develop long, 

 straight, rooting columns l ) (fig. 3), formed of a bundle of as many as 8 kenozooecia, which 

 diverge when they reach the substratum, sometimes separating from one another to form 

 irregular attaching processes. These may give rise to isolated, free peristomes, which reach a 

 considerable length (350. O 2 ). 



The largest specimen found (412. A.) consists of a colony about 45 mm. in diameter. It 

 is completely overgrown by, and embedded in a Sponge, so that its form cannot be made out. 

 On isolating one or two branches of this colony by means of Eau de Javelle, it was found that 

 the peristomes were of unusual length, and that they were to a considerable extent discrete ; — 

 probably as a result of an attempt to keep pace with the growth of the including Sponge. 



The ovicells are generally about as long as three series of zooecia of each side (fig. 4); 

 their frontal surface being only slightly convex. In some colonies, as shown in the figure 

 referred to, they are "simple"; i. e., not extending into a bifurcation. The ovicell appears to be 

 a modification of a median zooecium. Its ooecistome, when typically developed, is a beautiful 

 urn-shaped structure, with its basal region much dilated and porous; then contracting slightly, 



1) As in Idmonea radicata Kirkpatiick (1888, p. 83, PI. IX, fig. 2), with which this species may be identical. Similar rooting 

 columns have also been described, in /. pedata^ by Norman (1909, "Pol. Madeira", J. I.inn. Soc, Zool., XXX. p. 279. PI. XXXIII, figs 6, 8). 



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