No. 398.] REVIEWS OF RECENT LITERATURE. 155 
Grafting and Regeneration in Hydromeduse.— An interesting 
series of experiments on grafting and regeneration of Hydromedusz 
has been carried out by C. W. Hargitt! Small pieces of vigorous 
hydroid stems were held together in different positions by slivers 
of lead and were thus readily grafted. The bells of Gonionemus 
were emarginated so as to check their spontaneous movements and 
were then held together in pairs in various positions by being strung 
on bristles. As a result of these experiments, it was found that 
pieces of hydroid stems united with one another with great freedom 
either orally or aborally, and thus gave evidence of no polarity. The 
success of the experiments was quite independent of the sexes of the 
individuals from which the parts came. While pieces from closely 
allied species could be intergrafted, material representing different 
genera did not respond successfully. The experiments on the 
medusz showed that though these animals regenerated and grafted 
freely, aboral grafts were never successful, the animal thereby show- 
ing a marked polarity. CH, P: 
Regeneration in Grafted Tissue. — As is well known, the tail of 
one species of tadpole may be grafted on the body of another, and 
the two parts in time form an effective union. If the two species 
used have characteristically different kinds of pigment, the fate of 
the tissues thus brought together can be easily followed. The 
grafted ectoderm eventually covers. only the tip of the developing 
tail, whereas the grafted mesoderm forms a considerable part of that 
organ, z.e., at the beginning of grafting, the grafted tissues are sepa- 
rated kan the stock tissues by a single transverse plane; later the 
plane of separation between grafted ectoderm and stock ectoderm is 
much posterior to that between the two kinds of mesoderm. Grafted 
i tails when cut off regenerate, and the results of this process have 
been studied by T. H. Morgan? If cut transversely, the cut surface 
from which regeneration will take place may exhibit a face of ecto- 
derm from the stock and of mesoderm from the graft. The grafted 
tail may be cut obliquely, so that the cut surface will exhibit stock 
and graft ectoderm and graft mesoderm. In all these cases the 
regenerated tails are composed of cells easily referable to their 
Sources, and it may be concluded that in regeneration from a region 
:2.7 2 ? e POG h 2" 
1 Hargitt, cw. E i tal Studies upon Hyd d 
vol. i, No. I, pp. 37-51. October, 1899. 
? Morgan, T. H. Regeneration of Tissue Composed of Parts of Two Species, 
Biological Bulletin, vol. i, No. 1, pp. 7-14. October, 1899. 
