384 Bemarks h/ Mr. 11. .1. Carter. 



other on the mitre-shaped inflation of the head, and not four 

 above and four below, as delineated by !Mr. Hip:2;in (PI. XXI. 

 fig. 10) from the spceimen of Ifi/a/onema Sicholdll in the 

 Liverpool Free Museum. This shows that, besides /owr arms 

 recurved and opposite on a niitre-shaped inflation being the 

 princij)le on whieli the head of the anclioring-sj)ieule is formed 

 generally in the Ifi/aloncmafd, it is subject to the modifications 

 mentioned in all these si)eciinens. 



As regards the bearing of this " principle of formation " 

 on the termination of the anchoring-spicules of the genus 

 Bossella^ in which there are also four opposite arms, it will 

 be seen by comparing the two that there is no " inflation " 

 in BosseUdj but the arms come off from the end of the spicule 

 directly ; also that the diameter of the head, taken in its en- 

 tirety, is for greater than that of any part of the shaft — which 

 is the opposite in Hi/ahneina^ in which the so-called " arms " 

 are little more than spines, while in Bossella, from their size 

 and length, they are really " arms ;" lastly, that the shafts of 

 the anchoring-spicules in the genus Bossella are not spined, 

 but smooth. 



The large " birotulate, no. 11 ," p. 380, appears to be the full- 

 grown size of the minute or embryonal one " no. 13," as evi- 

 denced by gradationary development in a fragment of Hi/aIo~ 

 nema Sieholdii mounted in Canada balsam ; while the dif- 

 ferences in form do not amount to more tlian modifications of 

 the normal type — consisting of a shaft, and eight arms opposite 

 and recurved, all round each end ; which arms being knife- 

 shaped Avith their thin edges respectively extended into a 

 falcate form towards the shaft, with which they are thus 

 united, constitutes this flesh-spicule the representative among 

 the Hexactinellid sponges of the common equianchorate. 



The " spinicruces " of Brandt, so well figured by Dr. 

 Bowerbank (Brit. Spong. vol. i. pi. vi. figs. 153-1.07, p. 252), 

 have their representatives, as stated by 3Ir. Higgin (p. 381), 

 in the crucial spicules with spined extremities, so abundant 

 just where the sponge-head joins the cord in Hyalonema 

 cebuense (PI. XXII. fig. 2). 



They are sirailarlv situated in //. Siehohlii and in //. /w,s/- 

 tanicum ; but we do not find that they extend upwards further 

 than this. 



In some very small specimens of //. hisitanicum dredged 

 up oft' the Butt of the Lewis on board II.M.S. ' Porcupine ' 

 both with and without the Polype, these spicules are equally 

 abundant at the point mentioned ; while the cord in //. hisi- 

 tanicum, not stopping halfway up the sponge-head as in 

 n. SidiolJiij but passing entirely through the head so as to 



