290 The American Naturalist. [March, 
no trace of the multipolar inwandering of cells as described by 
MeMurrich. 
In the formation of the Scyphistoma it is found that the planula of 
A. marginalis settles down by the aboral pole which is peculiarly mod- 
ified. 
In all the species examined the mantle is a new formation and not a 
reopening of a gastrula mouth. 
The inrolled part of the ectoderm remains as the esophagus, and is 
not invaginated again, so that there is no doubt of the correctness of 
the views held by Goette regarding the ectodermal nature of this part 
of the digestive cavity. . 
The first pair of gastric pouches arises as a pair of outgrowths from 
the entoderm, but the second pair comes from the ectoderm. 
The ectoderm thus takes part in the formation of the esophagus, 
the septa and the gastral filaments as well as the second pair of the 
four original pouches. 
Goette’s views as to the relation of the Hydromeduse and Anthozoa 
are thus strengthened by these observations. 
Blastomeres of Medusz.—Raffaello Zoja, of Pavia, has pub- 
lished a preliminary notice’ of some most interesting work upon the 
development of isolated blastomeres of Medusz and of other non-ver- 
tebrates. He finds that even ys of an egg, that is, one of the isolated 
cells when the eggs has divided into 16, is able to develop by itself into 
a perfect organism; it develops in the same way as a complete egg 
and forms as perfect an individual. 
In Clytia flavidula }, ł, $ or rs when isolated develops into a hollow 
blastula in which entoderm arises by migration. A larva results that 
differs from the normal whole-egg-larva only in size. In the case of 
} or } egg the hydroid form was ultimately obtained. The larva prob- 
ably has half as many cells as in the normal case. 
In Laodice cruciata also 3, 3, $ or rs of the egg will grow into a 
perfect, but small swimming larva. 
In Mitrocoma anne } or ł of the egg gives rise to a perfect larva. 
In Liriogie micronata one of the first two or the first four blastomeres 
may form by delamination a larva with ectoderm and entoderm. In 
the former case a medusa with the symmetrically arranged tentacles of 
the adult may result! 
The isolated pieces of meduse eggs develop like the whole egg and 
not like parts regenerating the rest. 
7 Anatomischer Anzeiger X, Oct., 1894. 
