THE AXIAL GRADIENTS IN HYDROZOA. 2O5 



tion of these anesthetic agents shows a basipetal gradient like 

 the primary gradient. 



The second conclusion from these experiments is that disinte- 

 gration and death are retarded in those regions which are para- 

 lyzed immediately or very early, as compared with those regions 

 which show marked muscular activity before paralysis, so that 

 disintegration may begin in the body below the tentacles (Fig. 

 65), and often also in the stalk, while the tentacles are mostly 

 and the hypostome wholly intact. 



The course of disintegration in methylene blue and Janus 

 green is essentially the same as in alcohol and ether. In these 

 dyes, however, the excitation is more marked and in the lower 

 concentrations (methylene blue, 1/10,000 or less, Janus green 

 1/50,000 or less) may continue for hours, but is finally followed 

 by paralysis and rigidity in a state of more or less extreme con- 

 traction. This paralysis and rigidity, which perhaps resembles 

 muscle rigor, appears first at the tips of the tentacles and pro- 

 gresses basipetally in tentacles, body and stalk. The motor be- 

 havior in these dyes consists at first merely of elongation, con- 

 traction and other movements of all parts, but as staining pro- 

 gresses, the behavior comes to resemble more and more closely 

 ' the disgorging reaction of normal animals. The mouth becomes 

 permanently open, the hypostome flattened, the tentacles stand 

 at right angles to the body, and the body itself undergoes re- 

 peated contraction, while the stalk is much less active and only 

 very gradually attains a strongly contracted state. It may be 

 noted that these dyes accumulate in the entoderm as rapidly as 

 or even more rapidly than in the ectoderm, and the entoderm 

 often begins to disintegrate before the ectoderm. To all appear- 

 ances they irritate the entoderm and so give rise to the disgorg- 

 ing reaction. But whatever the exact physiological condition 

 may be, these dyes produce relatively early paralysis of tentacles 

 and hypostome, extreme activity of the body and less activity 

 of the stalk before the final rigidity death and disintegration 

 occur. As regards the course of disintegration, the result is 

 much like that in alcohol and ether, disintegration beginning in 

 the body below the tentacles and progressing basipetally while 

 the tentacles are mostly and the hypostome wholly intact (Figs. 



