120 Mr. H. J. Carter oti 



23. Polymastia bico/or, var. crassa. 



The same, with only three or four processes of much 

 greater length, one of which is 2 in. long by i in. in diameter 

 at the base. 



Ohs. Not being able at first to see any vents about the 

 specimens, which, as before stated, present a more or less 

 areniferous dermal coat of a yellow colour over the basal 

 structure, that is between the bosses or mamilliform appen- 

 dages, I slit open the largest process of no. 23, and found 

 that the excretory canal commenced in small branches towards 

 the summit, in a spongy tissue which, formed of a labyrinthic 

 hypertrophy of the pore and subdermal cavity-structure, filled 

 up the end and sides of the mamilliform extension ; and 

 tracing these downwards by means of their size and the 

 subcircular folds which characterize an excretory canal, they 

 were observed to unite into a single trunk, which, when 

 pursued through the yellow tissue of the body, was found to 

 end in a vent situated laterally towards the base of the speci- 

 men ; thus affording still another instance of a direct com- 

 munication between the pore and subdermal cavity and the 

 excretory canal-systems at the surface of a sponge. This was 

 also found to be the case in the bosses of Polymastia hicolor 

 and in the mamilliform processes of no. 22. 



There is a dry specimen of Polymastia hicolor among the 

 late Dr. Bovverbank's specimens from the south coast of 

 Australia, now in the British Museum ; but it must have 

 been much larger when fresh, for it is now \\ in. high by 1\ 

 X 5i horizontally. Indeed there are so many specimens of 

 this species in Mr. Wilson's collection that it, like many 

 others, must be very abundant about Port Phillip Heads. 

 Dr. V. Lendenfeld states that his Aplysilla violacea covers 

 '' many thousand square metres in Port Phillip " (Proc. Linn. 

 Soc. N. S. Wales, vol. ix. p. 311). 



Here I would observe with reference to a former state- 

 ment as to the "vents" of Desmacidon Jeffreysii^ Bk.= 

 Oceanaina^ Norman, not having been discovered (' Annals,' 

 1882, vol. X. p. 119), that it is just possible that they 

 may be found on a level with the surface of the sponge quite 

 independently of the long tubular appendages, which, being 

 in structure very much like the mamilliform processes of 

 Polymastia^ may in like manner be simply for inhalent 

 purposes ; except by accident, when the end of the tube may 

 be converted into a vent. 



