KOFOID: DEVELOPMENT OF LIMAX. 95 
or even clearly present this view, though he repeatedly calls attention to 
the lack of a sharp differentiation of the cavity from. the protoplasm of 
the most recent derivative or derivatives of the macromere. The fact that 
this gradual transition is shown toward two cells, as in his Taf. XII. 
Figg. 14 a-g, and Taf. XIII. Fig. 18 b, militates against the view that the 
savity is intracellular. It may well be that the yolk-laden macromere, 
on account of its different stainability, is more sharply marked off from 
the cavity than the protoplasmic micromere ; but is it not possible that 
the gradual transition of the granular protoplasm of the adjoining cell 
into the clear space of the cavity is in most, if not all, of the cases figured 
by Stauffacher due to oblique sections of the limiting membrane? His 
figures of the whole egg are made from reconstructions on glass plates, 
and in them the outlines of the cavities are not distinctly traced. In 
most cases he has not indicated the planes of the sections which he 
figures ; these must therefore be inferred from the position of the nuclei, 
Such inferences, however, lead one irresistibly to the conclusion that the 
sections must meet the boundary of the cavity obliquely wherever its 
outline appears indistinct ; e. g. Taf. XIT. Figg. 14 a-g; Taf. XIII. Figg 
184 and b On the other hand, sections which appear to strike the 
cavity perpendicularly, as in Taf. XII. Figg. 154 and b, 16 a and b, and 
17 a, all show a much more distinctly marked separation of the proto- 
plasm of the cells from the cavity, and in some cases this demarcation is 
as delinite on the side of the most recent micromere as it is upon that 
of the macromere, In case this explanation should prove valid, we shall 
have in Cyclas, as in Limax, an intercellular cavity appearing at the 
two-cell stage, and recurring in the later stages of cleavage. 
I cannot agree with Stauflucher's view that this primitive “haller 
Raum” has nothing whatever. to do with the true cleavage cavity. It 
is not established even by the facts found by him in Cyelas ; much less 
by a comparison with other forms presenting a similar phenomenon, 
His observations are confined to killed, preserved, and hardened material 
of very limited amount. Ile had in some cases not more than one series 
of sections of each cleavage stage; of tho three-cell stage seven series, of 
the four-cell stage six series. Ife has not been able to examine the epus 
in the living state, or in whole preparations. Thus he has been deprived 
of most valuable assistance in determining tho origin, definite bounda- 
ries, successive phases, ultimate fate, and relationships of this “ heller 
Raum,” whose claim to the title of cleavage cavity he so summarily 
dismisses, The “unumstosslich Beweis” which he brings forward to 
support the view he advances is, that the “heller Raum ” finally dis- 
