July 3, 18^.] 



SCIENCE, 



has recently received important extensions 

 through the noteworthy experiments of Nuss- 

 baum ^ and of Gruber,-^ who have demonstrated 

 independent!}' the possibilit}" of dividing uni- 

 celhilar animals so that each piece will regen- 

 erate the missing parts. In this manner the 

 number of individuals can be artiticially multi- 

 plied. For example : Nussbaum divided a 

 well-isolated Oxytricha into two equal parts, 

 either transversely or longitudinalh', and found 

 that the edges of the cut became soon sur- 

 rounded with new cilia. Although some of the 

 substance of the bod}', or even a nucleus, was 

 lost through the operation, 3'et, by the follow- 

 ing da}', the two parts converted themselves 

 into complete animals with four nuclei and nu- 

 cleoli (nebenkerne) and the characteristic cili- 

 ary apparatus. ''The head-piece has formed 

 a new hind end ; the right half, a new left half." 

 The new-formed duplicate Infusoria multiplied 

 subsequently by spontaneous division. From 

 one Ox3'triclia cut in two, Nussbaum succeeded 

 in raising ten normal animalcules, which sub- 

 sequenth' all encysted. After an unequal di- 

 vision, the parts are both still capable of 

 regeneration, but parts without a nucleus did 

 not survive ; which suggests that the formative 

 energy is in some way bound up with the nu- 

 cleus. But nucleate pieces may break down. 

 Thus all attempts at artificial multiplication of 

 the multinucleate Opalina failed, although the 

 division of Actinosphaerium had been success- 

 fully made by Eichhorn as long ago as in the 

 last centur}'. Pelomyxa palustris has been suc- 

 cessfully divided by Greef, and Myxastrum 

 radians by Haeckel. 



Gruber (L c, p. 718) describes his experi- 

 ments with Stentor : " If one divides a Stentor 

 transversely through the middle, and isolates 

 the two parts, one finds on the cut surface 

 of the hind part, after about twelve hours, a 

 complete peristomial field with the large cilia 

 and buccal spiral newly formed. On the other 

 hand, the piece on which the old mouth is 

 situated has elongated itself backwards, and 

 attached itself in the manner peculiar to these 

 Infusoria. If one has made a longitudinal sec- 

 tion, so that the peristom is cut in two, then 

 the peristoms both complete themselves, and 

 the lateral wounds heal over. I have repeat- 

 edly separated by trans-section pieces consider- 

 ably less than half of the original Stentor, and 

 these have also regenerated themselves to com- 

 plete animals." Gruber, too, observed that 



1 M. NussBAr^i. Uebfr spontane und kunsiliche zelltheil- 

 ung. Sitzungsb. Niederrhein. ges. nat. u. heilkunde. Bonn, 

 Dec. 15, 1884. [I regret very much that I know this jiaper only 

 hy Grut)er'8 abstract.] 



2 A. Gruber. Ufhfir kunHliche Udlung bei Infasorien. 

 Biolog. centralbl., iv, (No. 23; 717-722. 



artificially divided Infusoria were capable of 

 subsequent spontaneous multiplication. If the 

 section is not very deep, there may arise double 

 monsters ; but here, just as in spontaneous 

 divisions, as long as there remains an organic 

 connecting-band, the two parts act as one in- 

 dividual, showing that the nervous actions are 

 not restricted to determined paths. Gruber 

 also adds, that two divided pieces may be re- 

 united, if they are brought together again 

 quickly enough. The observation thus briefly 

 announced is of such extreme interest and 

 importance, that the publication of the full de- 

 tails of the experiment will be eagerly awaited. 

 Gruber adds, that at present we cannot go 

 much beyond the proof of the existence, to a 

 high degree, of the regenerative capacity in 

 unicellular organisms. He also makes the sig- 

 nificant observation, that, in the Protozoa, we 

 have to do foremost with changes of function ; 

 in the Metazoa, with growth also. 



2. Duplication of parts. In these anoma- 

 lies we find an organ which, although an extra 

 member,' yet still conforms to the type of the 

 species. For example : a frog is found with 

 three posterior limbs ; dissection proves the 

 third leg to agree anatomically with the tj'pi- 

 cal organization of the frog's hind leg. In 

 determining the importance to be attributed to 

 this evidence, it should be remembered, on 

 the one hand, that these instances are by no 

 means unusual ; on the other, that the agree- 

 ment with the normal structure is not uniform. 



3. Asexual reproduction. When a species 

 multiplies by fission of any kind, we must as- 

 sume that each part, after division, possesses 

 the formative tendency, since we see it build 

 up what is necessar}^ to complete the tj'pical 

 organization of the individual. Again : a bud 

 of a hydroid or polyzoon, although comprising 

 only a small part of the body, is equall}' en- 

 dowed with this uncomprehended facult}'. In 

 pseudova we reach the extreme limit : in 

 Aphis, for example, the parent gives off a 

 single cell, the capacity of which to produce 

 a perfect and complicated individual, fullv 

 equals the like capacity of a hydroid bud or 

 of half a worm. 



The evidence forces us to the conclusion 

 that the formative force or cause is not mereh' 

 the original disposition of the forces and sub- 

 stances of the ovum, but that to each por- 

 tion of the organism is given, 1. The pattern 

 of the whole organism; 2. The partial or com- 

 plete power to reproduce the pattern. The 

 italicised formula is, of course, a veiy crude 

 scientific statement, but it is the best which 

 has occurred to me. 



