244 



SCIENCE. 



[N. S. Vol. XIV. No. 346. 



In the annelids we find a great many- 

 forms that regenerate — many marine poly- 

 chseta have this power ; all earthworms 

 that have been studied regenerate; both 

 land forms, as lumbricus, allolobophora, 

 etc., and fresh- water forms, as 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 myriopods 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, as 

 caterpillars, mantis and the cockroach. The 

 large majority of insects, in the imago state, 

 do not seem to be able to regenerate, 

 although they have not been sufficiently 

 examined. . 



In the molluscs regeneration of the head 

 takes place under certain conditions. 

 Spallanzani thought that if the entire head 

 is cut off a new one regenerates. This con- 

 clusion was denied by at least eleven of 

 his contemporaries and confirmed by about 

 ten others. It was found later that the re- 

 sult 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 regeneration 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 the foot re- 

 generates also in the fresh-water snails, 

 physa, limnoea 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 hec- 

 tocotylized arm. 



In all the main groups of echinoderms, 

 with one possible exception, regeneration 

 has been found to take place. Probably all 



starfishes and brittle- stars regenerate their 

 arms, and even if cut in two or more pieces 

 new starfishes develop. The crinoids regen- 

 erate lost arms, and even parts of the disc ; 

 also the visceral mass. The holothurians 

 have very remarkable powers of regenera- 

 tion. In some forms regeneration takes 

 place if the animals are cut in two, or even 

 in more than two pieces. ' The remarkable 

 phenomena of evisceration that take place 

 in certain holothurians, if they are roughly 

 handled, or kept under unfavorable condi- 

 tions, are well known, and have been de- 

 scribed by a number of writers. It has even 

 been suggested that the holothurian may save 

 itself by offering up its viscera to its assail- 

 ant ! Unfortunately for this view, it has 

 been found that the viscera are unpalatable, 

 at least to sea-anemones and to fishes. 

 Ludwig and Minchin suggest that the 

 throwing off of the cuvierian organs, that 

 are attached to the cloaca, is a defensive 

 act, and if carried too far, according to the 

 latter writer, the viscera may also be lost. 

 ■ The holothurians have remarkable recuper- 

 ative powers and may regenerate new vis- 

 cera in a very short time. The sea urchins, 

 form, perhaps, an exception in this group 

 since there are no records of their regener- 

 ative power, but no doubt this is because 

 they have not been as fully investigated as 

 have other forms. 



In the vertebrates we find that the lower 

 forms, amphioxus, petromyzon and sharks, 

 have not been studied in regard to their 

 regenerative power. In the teleostean 

 fishes, the fins of a number of forms have 

 been found to regenerate. It is probable 

 that this takes place in most members of 

 the group. 



In the amphibia we find a large number 

 of forms that regenerate their limbs and 

 tail, and other parts of the body, but lim- 

 itations appear in certain forms. The rapid 

 regeneration of the legs in the smaller uro- 

 deles has been often described. In larger 



