240 BULLETIN OF THE 
or closely related to Agalma, to know accurately the changes in external 
form which the ovum passes through in these genera. Upon such knowl- 
edge we can hang our speculations regarding the possible descent of the 
members of the Siphonophora one from another, or from a common 
ancestor. 
The species of Agalma which has been studied is the only Agalma 
thus far recorded from New England waters. It is called Agalma ele- 
gans, and was first described by the author. When this animal was first 
taken, in 1876, I regarded it as the same as the “form (b) ” of Agal- 
mopsis elegans Sars, or closely related to it. 
Early Changes of the Egg before Segmentation. 
The earliest changes in the egg take place, in all cases observed, 
while it is enclosed in the female gonophore.* These go on with great 
rapidity, as will be shown by the following statements. Specimens of 
Agalma captured on August 6, at noon, were found four hours later to 
have dropped their gonophores, from which had come ova segmented 
in the 4-cell stage. It must be mentioned, however, that by transfer- 
ring the Agalma from the sea into aquaria they were placed in unnatural 
conditions, so that changes in temperature and other causes may have 
accelerated or retarded their rate of growth. There is nothing to show 
that there are not other kinds of segmentation besides that which is 
here described. 
* In a popular article on the development of Agalma elegans, published in the 
American Naturalist for March, 1881, certain changes in the germinative vesicle 
which were mistaken for segmentation were spoken of. This interpretation was 
erroneous, and the true segmentation was not described. On p. 188, op. cit., the egg 
is spoken of as cast into the water and there impregnated. There is nothing to prove 
that this is the case in Agalma. It has, however, excellent support in the history 
of observation. Gegenbaur, Beitriige zur niheren Kenntniss der Schwimmpolypen 
(Siphonophoren), p. 49. Writing of the genera Agalmopsis, Forskalia, Physophora, 
Hippopodius, and Diphyes, he says: ‘‘ Die Befruchtung erfolgt erst nach dem Aus- 
tritte der Eier aus der Eikapsel ; denn niemals fand ich Samenfaden in letzere einge- 
drungen, eben ausgetretene Eier dagegen stets von ihnen umschwirmt. Sie sassen 
dann strahlenartig mit dem Képfehen an der Peripherie des Eies an, mit dem Faden- 
theile selbst in zitternder Bewegung.” I have not been able to observe a similar 
condition in Agalma, nor was a free egg with nucleus and nucleolus found floating 
in the water. In one instance these bodies were observed to vanish while yet the 
ovum was inits gonophore, while the stalk of the same was attached to the parent. 
All eggs found free from the gonophore are destitute of these structures. 
ao 
