RHABDOCALYPTUS CAPILLATUS. 283 



of fibers (PL XXII., fig, 16). In each such system, the most 

 superficially situated head or heads, generally 1-3 in number and 

 belonging to the oldest hypodermalia in the group, consist of rays 

 which exhibit the spines ; all the more deeply lying and succes- 

 sively younger heads are made up of smooth rays. From the 

 center of the radiate hypodermal system arise the prostalia in a 

 tuft, the base of which is enveloped in the papilla-like prominence 

 of the dermal surface. A number of comitalia accompanying the 

 shafts and those of certain more or less radially dis[)osed parenchy- 

 malia extend their distal ends into this papilla-like base of the 

 prostalia. The prostal pentactins, being nothing else than old 

 hypodermal pentactins protruded through the dermal layer, need 

 not be specially described. 



Diactins do not seem to associate with the hypodermal 

 paratangentials in forming the support to the dermal layer. 



It may be worth mentioning here that in the smallest specimen 

 I have had — measuring only 3 mm. across the body — the small 

 hypodermal pentactins were all found to have regularly cruciate 

 paratangentials. This may be explained by the f^ict that they 

 were situated isolatedly and hence there were wanting in their close 

 proximity shafts of older pentactins, the presence of which shafts 

 should cause the paratropism of the younger pentactin-heads. 

 None of the hypodermalia in this little specimen were protruded 

 as prostalia, nor were any of them as yet in possession of the 

 spines. 



The Jiypogaslnd strands consist of diactins, essentially the 

 same as those which make up the parenchymal bundles. 



The dermalia (PI, XXII., fig. 6) are (juite predominantly 



