CTENOPHORA. 



that it takes any kind of animals which it may have occasion to catch. That its tentacles must 

 afford a rather powerful catching instrument is evident from the fact that it can capture animals 

 with so strong powers of movement as shrimps. 



The tentacles (PI. I, PI. Ill, Figs. 7, 10, 12) are simple, without accessory filaments. They 

 are rather variable in thickness, on account of the different stages of contraction on preservation. 

 The tentacle basis is short and rounded, slightly lobed where the tentacle proceeds (PI. Ill, Figs. 10, 12). 

 In a few instances I have observed a small secondary tentacle below the primary (PI. Ill, Fig. 12). 

 The whole tentacle apparatus is of a conspicuous yellow colour, due to the colloblasts which cover 

 both the basis and the tentacle, as usual in the tentaculate Ctenophores. The colloblasts (PI. VIII, 

 Fig. 8) are of the typical form; the spiral filament is inserted in the muscle layer of the tentacle in 

 the usual way; the central filament appears to be short. For finer histological observations on the 

 structure of the collobasts the material was, of course, not suited. 



In sections the axis of the tentacle is seen to consist of a solid muscle cord (PI. V, Fig. 2 t. 

 PI. VI, Fig. 3 t. PI. VIII, Fig. 4), without any special central core as is found in the primary ten- 

 tacle of Coeloplana, according to Abbott 1 ). The structure of the tentacle basis is shown by 

 the figs, i 7, PI. V, and especially by figs. 7 and 9, PI. VI. As appears [from these figures the 

 structure is in its main features in full accordance with that described by Chun and Her twig for 

 Honniphora a. o. Cydippids. The muscle cord of the tentacle is seen (PI. VI, Fig. 9) to proceed from a 

 fanshaped root occupying the middle part of the tentacle basis. To each side of the tentacle root is 

 a cavity which may be traced by means of sections to the main vessel (PI. V. Figs, i 10); they 

 represent the tentacular vessels. They are lined with a high, more or less vacuolated epithelium 

 corresponding to that found in the ridges of the gastrovascular canals and in the genital organs (see 

 below p. 12). On the outer side of the whole is found a thick, very conspicuous layer of colloblasts *) 

 (PI. VI. Fig. 7), the formation of which is seen to proceed from the sides, the fully formed colloblasts 

 occupying the middle part, from which they gradually pass on to the tentacle as it continues growing 

 out from the base. At the inner edge the thick colloblast-forming layer is seen to pass directly into 

 the low epithelium, quite endothelial in structure, which lines the tentacle sheath. The finer histo- 

 logical structure of the tentacle root, and the development of the muscles of the tentacle I have not 

 been able to trace in a satisfactory way; it does not, however, appear to be exactly as described by 

 Hertwig (Op. cit.) in Callianira. 



The genital organs form one of the most prominent features of the animal and at first 

 sight appear to be of a structure quite unusual among Ctenophores. On a closer study, however, they are 

 found to be built after the usual Ctenophoran type, the only essential difference being that they are 

 here restricted to short, round bodies, while in the typical Ctenophores they continue along the meri- 

 dian vessels for a longer or shorter distance. By the reduction of the costse and the shortening of 

 the main (longitudinal) axis of the body it necessary follows that also the meridional vessels are 

 reduced and the genital organs, being bound to these vessels, must be located on the end of the inter- 



') James F. Abbot. The Morphology of Coeloplana. Zool. Jahrb. Abt f. Anat. Bd. 24. p. 59. 



2 ) It is this layer of colloblasts which Willey has taken for chloragogenous cells in Ctenoplana (A. Willey. Oil 

 Ctenoplana. Quart. Journ. Micr. Sc. N. S. Vol. 39. 1897). 



->* 



