184 



abnormal and pathological phenomena, and I have never seen any- 

 thing like them in material preserved fresh. The nucleus is always 

 at the base, and is spherical with a diameter scarcely more than half 

 of that of the ectoderm nuclei , containing a chromatin network irre- 

 gularly thickened at certain points, no two nuclei being exactly alike 

 in details. Above the nucleus, under the base of the collar, a clear 

 bright space is always present in the protoplasm , circular in outline, 

 of about the same size as the nucleus, and often containing 1 — 3 black 



Fig. 3. 



Fig. 2. 



granules. I am not certain as yet whether this space represents a 

 ))Centralkörper(f , or a kind of food vacuole , or whether it is in some 

 way connected with the movements of the flagellum and collar. Im- 

 mediately above this space , in the centre of the collar, is a dark spot, 

 from which the flagellum arises. The collar is thickened towards the 

 base and exceedingly thin towards the extremity. The flagellum is of 

 equal thickness throughout. 

 Naples, 27th Febr. 1892. 



List of works cited. 



1) Metschnikoff, Spongiologische Studien. Zeitschr. f. wiss. Zool. XXXII 

 (1879), p. 349. Taf. XX— XXIU. 



2) Bidder, Review of Dendy's »Monograph of the Victorian sponges. Part I 

 Homocoela«. Quart. Journ. Micr. Sci, N. S. XXXII. part 4. Oct. 1891. 



3) V n L e n d e n f e 1 d. Die Spongien der Adria, Part I. Zeitschr. f. wiss. Zool. 

 LIII. Bd. 2. Hft. p. 185—321. Pis. VIII— XV and Part 2, 1. c. 3. Hft. p. 361—433. 



4) Minchin, Note on Sievelike Membrane etc. Quart. Journ. Micr. Sci. N. S. 

 XXXIII. Part 2. Jan. 1892. 



