48 



W. WOODLAND. 



when they do the relation is purely an accidental one. This 

 occasional accidental relation apparently originates thus : the 

 young spicules arise eacli in a single cell situated in the 

 hypodermis, and in the majority of cases the portion of the 

 hypodermis containing this spiculiferous cell remains in its 

 ordinary position, but if, as sometimes happens (say in 20 per 



Semi-diagrammatic drawing of tlie hypodermis and cuticle of Pro - 

 neomeuia aglaophenise, illustrating the "carrying up" of the 

 spiculiferous cells and spicules by the hypodermal papillae. Tlie 

 figure (x 400 diam.) is composed of drawings of the actual objects 

 brought together into one field. In A the spicule is in its normal 

 position ; in B the scleroblast is being detached from the hypodermis; 

 in C the scleroblast has lost its spicule, this lying free as at K; in 

 D a scleroblast wilh a well-grown spicule has been caught up in the 

 young papillary elevation ; in E a fairly young spicule has been 

 carried up some distance by a papilla; in E the spicule has similarly 

 been carried up, but is older; G and H represent young papillae; 

 J a full grown papilla, wilh its pigmented swollen extremity lying 

 just below the outer limit of tlie cuticle. It must be understood 

 that normally the papillae and spicules are quite distinct, not being 

 in any way associated. L represents debris on the exterior of the 

 thick cuticle; M is the hypodermis. 



cent, of cases), it becomes raised up into a papilla, the spiculi- 

 ferous cell is inevitably carried up Avith it, and then the 

 spicule superficially appears to be a product of the papilla 

 (see the accompanying text-figure). The majority of the 

 spicules are quite separate from the papillae, but in those 

 cases in which they are associated the purely accidental nature 

 of this association is proved by the various positions which 

 the spicule assume relative to the papilla, these illustrating 

 the various stages of '' carrying up " referred to above. 



