X 



48 On the Skeleton o/" Euplectella aspergillimi. 



ever, and sponges of that character, the enclosing material is 

 added as the spicules are projected and placed in position, they 

 being of a form not able to hold together without extraneous 

 aid. But in the beautiful Eujplectella we have what does 

 not occur in sponges generally (if, indeed, it occurs at all 

 in any other species) — that a structure is built up after a par- 

 ticular design which, Avlien finished, is not added to, and 

 which with slight variations obtains in all specimens : the 

 wonderful basketwork made up by the interlacing or inter- 

 weaving of the unusually long fine arms or rays of the va- 

 rious spicules is capable of holding together of itself by rea- 

 son of its form ; and the cementing material cannot advan- 

 tageously be added until this is all complete ; but when the 

 whole structure has been finished according to the pattern 

 which is constant in the species, tiie vitreous coating may be 

 applied and the entire skeleton rendered rigid. Perhaps this 

 silicious cement is not added in some localities ; but in the ex- 

 amples from the Philippine Islands the un vitrified state appears 

 to be, as Dr. Semper suggests, the primary state. 

 I am, dear Mr. Moore, 



Yours very tnily, 



T. HiGGIN. 



EXPLANATION OF PLATE lU. 



Fig. 1. 1. Large spicules forming ground-plan of the "squarish areas " or 



meshes, showing the position they occupy with respect to each 



other. Diameter of shaft at thickest point -^^ inch ; length of 



each ti'ansverse arm about f inch ; length of each longitudinal 



arm about | inch. 

 Fig. 2. One of the spicules of the diagonal lines, showing three arms only 



produced. 

 Fig, 3. A spicule, showing a suppressed arm and an abortive arm. 

 Fig. 4. A spicule, showing one of the various ways in which the anus are 



bent to suit the pattern. 

 Fig. 5. One of the spicules of the ridges or frills. 

 Fig. 6. A spicule, with all the transverse arms suppressed. 

 Fig. 7. 7. One of the fine straight spicules which lie along the arms of 



the large spicules, fig. 1. 1. 

 Fig. 8. One of the smooth stout sexradiate spicules interspersed amongst 



the network. 

 Fig. 9, One of the attenuate sexradiate spicules, spined at the ends of the 



arms, found interspersed amongst the network and sarcode. 

 Figs. 10 & 11. '' Flesh-spicules," "rosettes." 



The spicules 8 and 9 are very frequently found with the short 



longitudinal arm suppressed. 



The figm-es represent the proportionate sizes of the spicules, 



with the exception of the smaller sexradiate forms, which are on 



a largrer scale. 



