42 GEORGE BIDDER. 
in other sponges there were in the chambers large masses containing hundreds 
of transparent globules (fig. 13 a) laden with small detritus. While their 
individual size and appearance strongly suggest ejecta from the cells (cf. figs. 
4 and 10), their large aggregate mass makes this supposition difficult without 
stronger evidence. 
Fic. 14.—From the same sponge after one day more in sea water. Most 
chambers showed perfectly normal collars and flagella; this (transitional ?) 
form occurred in several places. Flagella active. 
Fig. 15.—Series D of paraffin sections, preserved in osmic 1 per cent. at 
the time fig. 1 was drawn from the same sponge. ‘The cells are very unvary- 
ing throughout the preparation, fusion of collars being rare and difficult to 
find; it occurs in a few cells. (See also woodcut a, 4). 
Fic. 16.—A typical set of cells from another slide of the same series of 
sections as fig. 15; fixed with water, cleared in turpentine, passed through 
absolute, 90 per ceat., 70 per cent., 50 per cent., and 30 per cent. alcohol 
into Grenacher’s hematoxylin; after two minutes back in the reverse order, 
half a minute in 30 per cent. and some minutes in each of the other alcohols, 
mounted through turpentine in Canada balsam and chloroform. Perhaps a 
quarter of the collars in this preparation are unaltered in form, most are either 
shortened or constricted, some of the cell-bodies are contracted. 
Fic. 17.—S8. compressum. A Sollas’s membrane halfway up the collars, 
shown by careful focussing with the immersion lens to consist, as here drawn, 
of a series of bars and bands. With a dry lens it is seen as a strongly- 
stained line quite continuous round the chamber. 
Fics. 17 and 18 are from Series A; in about half the chambers the collars 
are separated, in about half united. Preservation as in text, except that the 
passage into alcohol was by 10 per cent. changes every ten minutes, and the 
tissue was eighteen hours in paraflin at 63° C. beforeembedding. These two 
sections stained on the slide in Grenacher’s hematoxylin and mounted in 
glycerine. 
Fic. 18 (v. supra).—Typical Sollas’s membrane, very frequent. The roughly 
shaded portion indicates the basal parts of cells above the focus, the under 
surface of the membrane being seen. 
Fic. 19.—S. compressum, living cells, flagella in movement. See fig. 20. 
Fic. 20.—Typical part of a section (Series B) made from the sponge from 
which fig. 19 was drawn; after preservation at the same time in osmic acid 
1 per cent. eighty minutes, 10 per cent. changes of alcohol every eight minutes, 
10 per cent. or 15 per cent. changes of benzol every quarter of an hour; 
stained on slide, Grenacher’s hematoxylin. 
Fie. 21.—Sollas’s membrane from a paraflin section of L. aspera; pre- 
served osmic acid 1 per cent., brought gradually through alcohols and decalci- 
fied with 1 per cent. formic acid in 90 per cent. alcohol, embedded through 
