1 04 RE GENERA T/OJV 



the jelly-fish, gonionemus, and certain members of the family TJiau- 

 mantida, have been found to regenerate. Amongst the Scyp/iozoa, 

 metridium, cerianthus, and the scyphistoma of aurelia regenerate, 

 and the jelly-fishes belonging to this group have a limited amount of 

 regenerative power. 



In the platodes we find that all the triclads, thus far examined, 

 including planaria, phagocata, dendrocoelum, and the land triclad, 

 bipalium, regenerate. It has been shown that the marine triclads 

 also regenerate, but less rapidly and extensively, while the marine 

 polyclads have very limited powers of regeneration. The regeneration 

 of the trematodes and cestodes has not, so far as I know, been studied, 

 neither have the nematodes been examined from this point of view. 



Some of the nemerteans regenerate, others do not seem to have 

 this power. A small fresh-water form, tetrastemma, that I examined, 

 did not regenerate, although some of the pieces, that were filled with 

 eggs, remained alive for several months. 



In the annelids we find a great many forms that regenerate 

 many marine polychaeta have this power; all oligochaeta that have 

 been studied regenerate ; both land forms, like lumbricus, allolobo- 

 phora, etc., and fresh-water forms, like lumbriculus, nais, tubifex, etc. 



In the Crustacea the appendages have the power to regenerate in 

 all the forms that have been examined. 



Several kinds of myriapods, as well as a number of spiders, are 

 known to regenerate their legs. In the insects, however, only a few 

 forms are known to have this power, caterpillars, mantis, and the 

 cockroach. The large majority of insects, in the imago state, do not 

 seem to be able to regenerate, although in a few cases regeneration 

 has been found to occur. 1 



In the mollusks, regeneration of the head takes place under certain 

 conditions. Spallanzani thought that if the entire head is cut off a 

 new one regenerates. This conclusion was denied by at least eleven 

 of his contemporaries, and confirmed by about ten others. It was 

 found later that the result depends in part on the time of year and in 

 part on the kind of snail. Carriere, who more recently examined the 

 question, found that even under the most favorable conditions regen- 

 eration does not take place if the circumoesophageal nerve-commissure 

 is completely removed with the head, but if a part remains, a new 

 head develops. It has been stated that a new foot regenerates in 

 helicarion, and I have found that the foot regenerates also in the fresh- 

 water snails, physa, limnsea, and planorbis. If the margin of the 

 shell of a lamellibranch or of a snail is broken off, it is renewed by 

 the mantle. The arms of some of the cephalopods are known to 

 regenerate, particularly the hectocotylized arm. 



1 For a review of the literature see Brindley, '98. 



