REPORT ON THE KERATOSA. 39 



influence of preservation in alcohol. I think that the colouring substance, by which the 

 sj)ongol)lasts (if not all the cells of lanthella) are coloured in the living state, is soluble 

 in spirit, and might thus when dissolved have coloured the true horny substance also ; 

 for, while I found most of the fibres of a violet colour, and containing violet cells, 

 I found also fibres whose cellular elements were of a deeper colour than usual, and that of 

 the horny laminee considerably paler. 



The Soft Parts. — As to the anatomy of its soft parts, the species differs but little 

 from AplysiUa, DendriUa, and HaUsarca ditjardini. Both the surfaces of the sponge 

 when examined with the naked eye show a great number of groups of openings, as 

 represented ou PL II. fig. 1, under a low magnifying power. These are the oscula, each 

 b eing usually represented by four or five apertures. The parts of the membrane 

 between them, when seen under the microscope, show themselves as usual to 

 be provided with numerous minute pores. The water entering through these porz 

 dermales reaches the cavities under the covering membrane, and passes from these latter 

 by means of pori camerales into the flagellated chambers, in order to be expelled 

 through a large mouth into exhalent canals, finishing with the oscula above mentioned. 

 Thus each osculum, with its pores and its subdermal or inhalent cavities, flagellated 

 chambers, and exhalent cavities, presents an independent whole, which may be compared 

 with a state in a federal republic. The inhalent and exhalent canals are of very irregular 

 outline ; they may be very large and short, very narrow and long, &c. 



The form of the flagellated chambers is also very variable. Its mathematical mean 

 shape is expressed by the two flagellated chambers on PI. II. fig. 5. But though such 

 regular pouch-shaped flagellated chambers may be found without difficulty, the outlines 

 of most others are quite irregular (comp. PI. II. fig. 4). Sometimes they are cylindrical 

 and elongated, sometimes irregularly roundish, often provided with secondary ramifica- 

 tions ; their size is inconstant. 



Now so far as the histological structure of the present species is concerned, it is 

 constant to the general type prevailing among the Keratosa, presenting, however, a few 

 new peculiarities. The ectodermic pavement-epithelium could be discerned only on the 

 surfaces of the inhalent canal system. My endeavours to make it out on the external 

 surfaces were unsuccessful, owing probaljly l^oth to the state of preservation and to 

 the fact that the external surfaces above mentioned are covered by a thin cuticle such 

 as Schulze^ has described in Cacospongia cavernosa. No distinction can be detected 

 between the ectodermic and endodcrmic pavement-cells. In all cases they are flat, irre- 

 gularly polygonal, with a comparatively small nucleus, and showing the protoplasmic 

 granules only around the nucleus. As to other representatives of the endoderm, viz., 

 flagellated cells, they seem to agree as regards their form with those of Ap>lysiUa^- but it 

 must be noticed that the flagellated cells are very sensitive to every method of preservation, 



1 Zeitschr.f. loiss. Zool, Bd. xxxii. p. 654. 2 ji,i£^ Bd. xxx., pi. xxiii. fig. 26. 



