E. W. BERGER ON THE CUBOMEDUS^E. 75 



Charybdea they lie wholly enclosed within canals of the supporting 

 lamella (Fig. 32, upper part). They run longitudinally, and near the 

 base of each tentacle pass out of their canals and become strictly 

 subectodermal (Figs. 31, 32). This is for Charybdea. In Tripedalia 

 they rarely come to lie in closed canals as in Charybdea. These 

 facts show beyond doubt that these muscles are developed from the 

 ectoderm. Claus has suggested their ectodermal origin, but did not 

 demonstrate it. He also suggested that they become inclosed in 

 canals by the supporting lamella pushing up around them and finally 

 fusing above them. This, I believe, is demonstrated by the conditions 

 in Tripedalia (Fig. 29). Here the canals usually remain open, but 

 occasionally, as in the left-hand canal, one may become completely 

 inclosed. This condition of things suggests the intra-lamellar muscles 

 found in actiniarians. The nuclei found in the canals with the muscle- 

 fibers probably belong to the cells from which the muscles become 

 differentiated. Claus figures these muscle-fibers and nuclei, and it ma} 7 

 be added that the supporting lamella he figures, for C. marsupialis, 

 is much thicker than I have figured it for C. Xaymacana and 

 Tripedalia cystophora. The number of muscle-canals also is greater 

 and occupies a much greater depth of the thickness of the lamella. 

 Since Claus gives a figure of a transverse section showing the muscles 

 in their enclosed canals, I have not deemed it necessary to duplicate 

 his figure. In the transition from a tentacle to a pedalium, the 

 muscles are most strongly developed toward and at the edges of the 

 pedalium. This is true for the pedalia in general, and accounts for 

 the readiness with which they can be bent inwards, as noted in the 

 physiological part of this paper. 



(c) I have found a single ganglion-cell among the cells of the 

 ectoderm of the tentacles. This showed so plainly that I have figured 

 it (Fig. 28). Other ganglion-cells no doubt exist, but could probably 

 not be distinguished from other cells. In its position in Fig. 28 it 

 appears to be associated with the nettle-cell shown just above it. Its 

 position is very much the same as that figured by Lendenfeld (25a). 



The Endoderm. The cells of the endoderm of a tentacle are 

 long and quite slender (Fig. 31). At their bases they are vacuolated 

 quite like the cells of the ampulla and the canal of the sensory 

 clubs. They contain a well-formed nucleus with a nucleolus. In 

 their distal half small light bodies with a dark center are very 

 evident. These bodies are evidently a secretion. 



