N'KW SPKCIFS or CI.'AWI.lNi; MKIMISA PROM AI'STHAI.IA — iiRirir;.';. 99 



tliey p;i()\v older it extends down ii slioit distanee on eaeli Hide of tlie 

 tentacle, never, however, reacliing so far as to become oral in position. 

 The third neniatocyst-cluster occurs on the ventral or oial side of the 

 branch ; it is sinallei- than the second, and is confined entiiely to the 

 ventral surface. A fourth cluster is aboral in position and is nsiially 

 se[)arated from the second by an interval whicli is either equal to or 

 sliofhtly less than the one winch separates tlie latter from the terminal 

 knob-like (!iustei'. The upper branch of the tentacle is thus armed with 

 four clnstei's, one teTininal, t wo aboial, one oi-al ; the last lyiiiff between 

 the two aboral, but nearer the [)roximal than the distal. 



In all the specimens examined the position of these nematocyst- 

 clusters on the upper branch of the tentacle was found to becoiistant. In 

 yonnjr individuals a small nematocyst-cluster occurs on the dorsal or aboial 

 side of the main stem a short distance from the point where it divides 

 int(t upper and lower branches, but in most of the adult sf)ecimens this 

 cluster is usually absent. It, however, is well developed in one specimen 

 with twenty-four tentacles (PI. xvii., fig. 1). 



Nematocvst-clustei's were never observed on the lower branch of the 

 tentacle. 



The nematocysts are of two kinds ; (1) large oviform nematocysts, 

 theii- length being 23-25 /<, and their breadth 17-19 ^^ ; and (2) smaller, 

 nari'owly oval or nearly cylindrical nematocysts, which measure 8 ji in 

 length and 4 fx in breadth. 



The lower branch of the tentacle, which is used for ci'awling, ends in 

 a sucker-like extremity. This expanded terminal part is strongly adhesive 

 owing to the presence of glandular cells in the ectoderm, while its sucker- 

 like action is brought about by the arrangement of the muscles in this 

 part. By means of these suckers and the secretion of the glands the 

 animal is able to adhere so firmly to the smoothest surface that it is 

 difficult to detach it. 



Fixation of specimens with hot sublimate-acetic causes very little 

 shrinkage of the tentacles ; both the nppei' and lower branches undergo a 

 slight but equal amount of contraction, so that in the pi-eserved state they 

 ptesent almost the same ap[)earance as in the living animal. This is 

 oontrar}' to the condition found in the Cape species, for here, according to 

 Gilchrist, the upper branch of the tentacle, which in the living animal is 

 about three times the length of the lower one, " ct>ntiacts much more in 

 pi'eservative, and is then only about the lengtli of the lower branch." 



The tentacles are hollow outgi'owths fr'om the outer wall of the 

 ciicular canal, the endodei-nial cells of which pass dii-ectly into the endo- 

 dei'mal lining of the tentacle. The lumen of the tentacle extends along 

 both the uppei' and lower branches. In the main stem the endoderm 

 consists of columnar cells, the nuclei of which lie close together neai- the 

 cell mai'gins which border lapon the narrow lumen of the tentacle. The 

 lumen of the lower branch is also very nari'ow, but the uppei' branch 

 contains a wide lumen, which is a i-ouspieuous feature in secti(»ns through 

 a tentacle. 



