On the Xnti-itice an<1 E.rci-etorij Procennes in Porifern. 48,'5 



Note on Sliogumi nitotestacoa, Lew. (Ann. Mai;. Nat. Hist, 

 scr. G, v.)l. iv. 1889, p. 274). 



Fairmairo in 188G described a species of Shoguna under 

 the generic names of Ilolocephala and Puchyceiihulu^ both of 

 which were preoccnpied, and in the Pascoc collection there are 

 .several species standing under the MS. name of Thione. The 

 genus seems to be represented by very numerous species in 

 many parts of the tropical and subtropical zones. In the 

 figure referred to above there are five joints given to the 

 hind tarsus, but under a high microscopic power only four are 

 visible. 



LIV. — 0)1 the Xutritivc and Excretory Processes in Porifera. 

 By Akthur T. Mastehman, J5.A., late fcjcholar of Christ's 

 College, Cambridge, Assistant Professor and Lecturer on 

 Zoology at the University of St. Andrews. 



An abundance of young colonies of many of the commoner 

 sponges in St. Andrews Bay gave opportunity for an inves- 

 tigation into the ])rocesses of nutrition and excretion as carried 

 on in the group Porifera. 



The experiments described below were carried out with 

 small colonies of Grantia compressa. Particles of carmine 

 were found to give the best result, although other colouring- 

 matters were tried. 



Tiie colonies were all placed in sea-water witii fine carmine 

 particles in suspension, and allowed to remain there for 

 two minutes ; they were then removed, washed, and placed in 

 sea-water. 



At the expiration of short periods of time, varying from 

 fifteen seconds to forty-five minutes, single colonies were 

 removed, killed in osmic acid, and sectionized. It was hoped 

 that a series of this kind would present a gradation of the 

 changes undergone by the particles during digestion and 

 excretion ; but, partly owing to the difficulty of washing 

 efi'eclually, and so keeping extraneous carmine from being 

 absorbed, and partly owing to a different rate of absorption 

 and digestion in colonies varying in size, the sections do not 

 show so distinct a gradation as was expected. The general 

 course of the metabolic circuit through the sponge can, how- 

 ever, be clearly made out. 



In figure 1, as in all the earlier sections, the carmine 

 particles are seen to be confined to the choanocytes, and in 



Ann. ds Mag. N. Hist. Ser. 6. Vol. xiii. 33 



