444 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
the eggs time to progress I discovered that they developed into normal 
planulae and thus was forced to conclude that this strange and irregular 
cleavage must after all be normal for the species. On several occasions 
the attention of a number of other observers, who were working in the 
same marine laboratory, was called to this phenomenon, and they also 
expressed surprise and remarked that they had never seen segmentation 
presenting such anomalous and irregular features. 
Metschnikoff describes and gives a few figures of a very similar 
condition of segmentation in Oceania armata. He says: “Wenn bei 
den beschriebenen Medusen verschiedene Abweiehungen in dem 
Zustandekommen des vierten Furchungsstadiums constatirt werden 
mussten, so konnte man doeh bei alien eine gewisse Regelmassigkeit 
auffinden. Ganz abweichend in dieser Beziehung verhalt sich 
Oceania armata, da bei dieser Meduse die kaum mit einander verein- 
igten Blastomeren durchaus unregelmassig und ordnungslos neben 
einander liegen.Das Abweichende in der Embryonalentwickelung 
der Oceania armata hort noch nicht so bald auf. Die Furchung 
setzt sich in unregelmassigster Weise fort und fiihrt zur Bildung 
unformlicher Zellenhaufen, in deren Innern Mann eine Furchungshohle 
durchschimmern sieht. Oft nehmen solche Embryonen eine ganz 
abenteurliche Gestalt an, deren Ursache zum Theil darin liegt, dass 
sie sich durch Theilung vermehren. Diesen Process habe ich an 
mehreren isolirten Blastula-Stadien beobachtet, so dass ich an dessen 
Existenz nicht zweifle.” In Turritopsis, likewise, the later cleavages 
take place in a most irregular manner and lead to the formation of a 
shapeless and grotescpie mass of blastomeres in which the cells are 
frequently held together very loosely. The accompanying drawings 
unfortunately represent only the most regular forms. This is due in 
part to the fact that the very irregular forms were at first thought, as 
stated before, to be abnormal; and partly because it was difficult to 
make accurate camera sketches of these shapeless masses during life 
while cleavages were taking place rather rapidly. 
Whether these embryos multiply by division, as Metschnikoff states 
to be the case with Oceania armata and to which he attributes in part 
the cause of their peculiar shapes, I have no direct evidence; but think 
that it is very probable that such may be the case. Frequently the 
blastomeres are separated into two distinct masses held together by a 
small isthmus of cells. If they do not divide by an internal activity, 
they must, occasionally at least, be broken apart by the action of the 
