150 ME. S. 0. BIDLET ON INCORPORATION 



of the microscope, is of a very elongated oval shape, sometimes of 

 irregular outline; the spicule diminishes iu diameter just below 

 the head, which is of about the same diameter as the thickest 

 part of the shaft, although, from its superiority in size to the 

 " neck," this is not at first evident. Had the spicule not been of 

 so interesting a type, it might perhaps have been set down as the 

 proper dermal spicule, as " occurring irregularly scattered or fasci- 

 culated," especially as a special dermal spicule is wanting, and 

 the dermis presents otherwise an unusually bare appearance. Also 

 the characters of the skeleton-spicule of the sponge would rather 

 lead oue to believe the dermal form to be merely one slightly 

 altered, owing to position, from its type, as its relative short- 

 ness (a character commonly distinguishing dermal and skeleton 

 spicules), identical thickness, and similar shape would lead one 

 to conclude. The skeleton-spicule is acuate, slightly bent, 

 sharply pointed, with a well-rounded basal end, without inflation, 

 size -577 by '01267 millim. 



However, a reference to sketches of the spiculation of another 

 sponge, an Esperia, from exactly the same locality, and obtained, 

 as its association in the same vessel with the Ciocalypta would 

 seem to show, at the same haul of the dredge, demonstrated an 

 identity in form between this spicule and the one which forms 

 the main skeleton and the dermal network of that sponge. As 

 the drawings were not both made to scale, measurement was ne- 

 cessary to satisfy the doubt as to the possible common origin of 

 the two spicules, with the result that the main skeleton-spicule 

 of this second was found to measure '544 by '01267 millim. ; 

 while the average largest size of the dermal spicules, which agree 

 precisely with the skeleton-forms as to shape and proportion, is 

 •468 by *01267, just the size, as will be seen by comparison with 

 the measurements given above for the spicule from the dermis of 

 the Ciocalypta, of the largest of those there discovered. The in- 

 ference is unavoidable, that the latter sponge has adorned and 

 strengthened its dermis with elements derived from the dermis 

 of the JEsperia, which probably grew close by, and which, from the 

 friable character of its surface, even in the spirit-specimen which 

 we possess, probably frequently lost its surface-spicules either by 

 attrition against tide-borne objects or by their natural shedding 

 in the course of growth. The former hypothesis is not an im- 

 possible solution, for the depth at which the sponges grew was 

 only 7-10 fathoms. Of their being lost by natural shedding, 1 know 



