208 
0. ARNOLD. 
the digestion in more highly organised animals such as 
Planaria. Moreover, the methods of research are necessarily 
different. In unicellular animals a considerable number of 
facts may be ascertained by the observation of the effects of 
intra-vitam staining. In animals such as the Planaria this 
is impossible on account of their lai’ge size and opacity. The 
observations here described have therefore been made upon 
carefully preserved specimens, and the staining reactions ai-e 
therefore post-mortem. 
The methods used were as follows : 
A number of Planaria lactea, which had been deprived 
of all food of any sort for fifteen days (after which period of 
time the cells of the intestine are entirely devoid of all food 
remains, see fig. 11) were fed with fresh clotted pig’s blood, 
and fixed in Flemming’s strong solution at various intervals 
after feeding. 
These intervals after feeding were as follows: j, i, IJ, 3i, 
27, 48, 52, 70, 76, 96, 118. When a Planarian has just fed, 
the fixation is attended with difficulty owing to the fact that 
immediately the animal is immersed in the fixing fluid it 
contracts and ejects the recently ingested food Avith consider- 
able violence, not through the pharynx, but anyAvhere through 
the skin. If, however, the animal is cut into several pieces 
at the same time that the fixative is poured upon it, this 
difficulty is partially obviated, the whole procedure being too 
rapid to permit of any violent contraction. Forty-eight hours 
after feeding the lumen of the intestine is almost empty, most 
of the blood having been ingested, and the Planaria fixed 
after that interval did not eject any of the remaining contents. 
The stains used were: (1) A triple stain — Basic fuchsin, 
methylene blue and orange G.,^ and (2) iron-alum-hmma- 
toxylin, acid fnchsin and orange G. 
All the figures, except fig. 5, are drawn from preparations 
stained by the former process. 
' I have given an account of tlie inethocl of using this stain in a 
paper on the “Ovi- ami Spermatogenesis of Planaria lactea," ‘ Arch, 
f. Zellforschung,’ Bel. iii, Heft 3, 1909. 
