SENSOE^Y REACTIONS OF CHROMODORIS ZEBRA 285 



The following notes are derived from observations with eleven 

 Chromodoris of medium size (10 to 14 cm. in length) into which 

 1 cc. of half-saturated strychnine hydrosulphate in sea-water 

 had been inj ected. This quantity was found by other tests not to 

 be fatal and to be the optimal concentration for our purpose. 

 The injection was made into the region of the heart, on the dorsal 

 surface. The behavior of each animal was studied individually, 

 before injection, during the action of the strychnine, and after 

 its effects had worn off. As a control, each individual was 

 studied in comparison with an animal into which 1 cc. of sea- 

 water had been injected. The latter operation had no detectable 

 consequences of any kind. Tactile activation was mostly used. 

 The results herein summarized are to be compared with those 

 given in the first section (p. 267). 



Following strychnine injection, the body remains for some 

 minutes much contracted, its surface being 'wrinkled' and thrown 

 into edematous blebs; the genital papilla is protruded, and the 

 posterior mantle glands are made prominent, owing to the forcing 

 of fluid into the spaces surrounding them. These effects appear 

 under any conditions leading to pronounced general contraction of 

 the body muscles. The gill collar, however, is strongly con- 

 tracted in a peculiar way, its edge being rolled outward. The foot 

 is folded together lengthwise and does not attach to the sub- 

 stratum. The gill plumes remain half contracted within the 

 branchial collar. The plumes tend to exhibit more or less rhyth- 

 mic contractions, followed by rapid but incomplete expansion; 

 perhaps this is in some way mechanically induced by the beat of 

 the heart, which distorts the neighboring dorsal integument. 

 The reaction of the gill plumes to shading is not apparent. 



After the lapse of half an hour to an hour in different indi- 

 viduals, the body is less strongly contracted, the gill plumes 

 more fully extended. The reactions of the plumes to touch are 

 curious and important at this point: to a single touch, a plume 

 reacts precisely as in non-strychninized individuals; but when 

 two successive touches are administered to adjacent plumes, the 

 reaction is of unexpected violence (fig. 6). A reaction of this 

 amplitude is obtainable in normal animals only by six or seven 



