KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 52. N:o (6. 65 
Anatomy of Madrella ferruginosa, 
A microscopical examination of sections through the notaeum gives some inter- 
esting results. Not only are the cerata empty, as Exnior (1913) states, and contain 
no liver diverticula nor any apical cnidocysts, but on the contrary these latter are 
included in cnidosacs situated at the bases of the 
cerata. Even by macroscopic examination one can 
perceive the openings of these cnidosacs at the tops 
of some small swellings at the side of the cerata 
(Pl. 2, fig. 68; text fig. 17). These small enidophor- 
ous sacs are combined with the liver diverticula by 
small canals. They are lined inwardly (fig. 18) with 
the characteristic cnidoblasts which are described by, 
for example, HeRDMAN 1890 and Hecut 1895 (=»né- 
matophages», CuzNnot 1907) and which are considered 
to be ectodermic cells by the first-named author and 
modified cells of the liver coecum by later scientists. 
That the latter opinion is the correct one is 
proved by the conditions prevailing in Madrella (fig. 
18). The ecnidophorous sac not only communicates _ 
with the liver coeca, but the cells of the former jim ie aE TE cok amen, 
gradually pass into those of the latter by means of {ve Hove; cot, ectoderm: i, liver calla 
the connecting collar cells. In this portion the cells : 
are shorter than the cnidoblasts described below, but in other respects they are 
similar to them; they also contain brown granulations, like the enidoblasts on the 
one hand and like the liver cells on the other, thus giving support for the supposi- 
tion not only that the cnidoblasts are modified liver cells, but that their granula 
are homologous with those of the last-named. 
The ecnidoblasts are long cylindrical cells with nearly basal oblong or pyriform 
nucleus. Above the nucleus they are filled with rounded, brownish granulations, 
which seem to be active by the arrangement of the cnidocysts in the cnidoblasts. 
They are to be found only in the innermost cnidoblasts and here only in their basal 
half, while the apical half is occupied by small ovoid vacuols enclosing the enido- 
blasts. The undermost of them are set with some small granula, but whether the 
enidoblasts are formed or only arranged by means of these granula, could not be 
made out from the present material. 
The ecnidophorous sac is surrounded with walls formed by unicellular muscles 
(fig. 14, musc.); the walls are thickest towards the base of the sac and grow thinner 
towards its apex. The muscle cells, which cross each other irregularly, extend down 
the collar and later on pass into the fibrillar cells which surround the liver diverti- 
cula. Even towards the apices of the cnidophorous sacs, the muscular cells pass into 
fibrillar ones, which are expanded beneath the epithelium. 
K. Sv. Vet. Akad, Handl. Band 52. N:o 16. 9 
