. The Journal of comparative neurology and psychology. ighting movements and the wormrolls over and over for a time. It then resumes creeping, usuallybackward for a time, then forward. In type V after the maximumstimulus and shrinking there occurs immediate rapid, forward creep-ing. It is manifest that shrinking movements interrupt, not tosay inhibit, movements of extension. In the weaker types of reac-tion II and III shrinking is more or less confined to the anteriorend as indicated by a momentary or temporary suspension of for-ward movement. In types IV and V the same condition is extendedov
. The Journal of comparative neurology and psychology. ighting movements and the wormrolls over and over for a time. It then resumes creeping, usuallybackward for a time, then forward. In type V after the maximumstimulus and shrinking there occurs immediate rapid, forward creep-ing. It is manifest that shrinking movements interrupt, not tosay inhibit, movements of extension. In the weaker types of reac-tion II and III shrinking is more or less confined to the anteriorend as indicated by a momentary or temporary suspension of for-ward movement. In types IV and V the same condition is extendedover the body more fully. Type IV shows that when extension is Harper, Reactions of Penchceta. 575 suspended at the more irritable ends it may continue in the type V indicates that when the whole body is involved mostcompletely in the shrinlving movement extension finds its first outletat the anterior end. Relation to the Musculatu7-e.—Certain anatomical features of themusculature need to be considered in connection with these types L. Fig. 1. This is to show the extent of circular and longitudinal musclesin different regions. A is from a section through the sixth segment fromthe anterior end; M, from a section in the middle region; P, from a sectionthrough the sixth segment from the posterior end; Ep, epidermis; C, circularmuscles; L, longitudinal muscles; S, muscles of the setae. of reaction. A comparison of a section through the sixth segmentfrom the anterior end with sections through the middle and the sixthsegment from the posterior end shows that the circular musculatureis highly developed in the anterior end, its thickness being twicethat in the other regions. The longitudinal musculature is ratheruniformly developed throughout the whole length. The reactionof type V involves the completest activity of the whole longitudinaland circular muscular systems, and under these conditions the anterior 576 Journal of Comparative ISfeurology and Psychology. end tak
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