BY R. VON LENDENFELD, PH.D. 485 



finest, measuring only 0-001 to such, measuring 0-Olmm.; all grada- 

 tions are formed, and the angles at the joining points of fibres of 

 unequal thickness are not equal. The fibres are formed in this 

 ■way, that the thinner one grows out from an already existing thick 

 one. The latter is straight at first, so that then the angles at the 

 sides of the newly formed thin fibre will be 90° each, and the third 

 angle 180.° 



As the young fibre grows in thickness it drav/s the other fibre 

 out of its straight course, so that the angles on the sides of the 

 young fibre increases, whereas the other one decreases. The three 

 fibres issuing from one joining point lie nearly in a plain, so that 

 the sum total of the three angles is nearly 360.° The distances 

 between the joining points of thin fibres are smaller than those 

 between the joining points of thicker ones, and in consequence of 

 this the network becomes irregular. Polejaefi"(l) gives a figure cf 

 thicker and thinner connecting fibres in Luffaria. Our sponges 

 have a very different skeleton, inasmuch as there are a great many 

 fibres of intermediate thickness, and not a system of thick and a 

 system of fine ones, as in that Luffaria. 



68. SPECIES. EQSPONGIA IRREGULARIS. Nova species. 

 In this species I distinguish the following four varieties : — 

 I. Euspongia irregularis silicata. 

 II. Euspongia irregularis lutea. 



III. Euspongia irregularis tenuis. 



IV. Euspongia irregularis Jacksonia. 



Shape and Size, 



The shape of the different varieties and even of different 

 individuals of one and the same variety, vary very much, so that 

 no diagnosis of it can be given. 



(1) N. PoUjaeff. The Zoology of the Voyage of H.M.S. Challenger. 

 Part XXXI. Report on the Keratosa, Plate IX., Fig. 5. 



