No. 11. — Studies from the Newport Marine Zodlogical Laboratory. 
Communicated by ALEXANDER AGASSIZ. 
XV. 
On the Development of Agalma. By J. Water FEwKEs. 
THE genus Agalma, in its growth from an egg into the adult, passes 
through three larval stages which can be readily distinguished from each 
other. These larvee, from the nature of the growth of the Agalma colony, 
are not separated from one another by clearly marked distinctions, but 
temporary organs found in one stage are often carried over to the next 
in the course of the passage of one larva into that next following. The 
peculiarities, however, of each are strongly enough defined to justify the 
division of the embryological history of Aga/ma into the three stages to 
which reference is made. 
These three characteristic larvee about which the young of the genus 
Agalma group themselves have been given the following names: 1. The 
primitive larva; 2. The Athorybia stage; 3. The larva like the adult 
in general features, although possessing together with organs of the 
adult certain provisional structures bequeathed to it from the earlier 
conditions of growth through which it has passed. 
The last two of these larval stages are not considered in this paper, 
except incidentally to record observations on certain appendages of the 
Athorybia stage, showing the fate of organs of permanent and others of 
provisional nature which play an important part in the appearance of 
the youngest or primitive larval condition. The present contribution 
deals with the outward changes in the growth of the egg from fertiliza- 
tion to the primitive larva. In that epoch many important organs, some 
of which persist into the adult, originate ; and, more significant still, at 
that time first arise the three layers out of which every organ of the: 
whole colony is developed. The development of the first of the three 
larval stages of Agalma may consequently be looked upon as a key to 
the phylogeny of the Oceanic Hydrozoa. It is therefore at all events 
necessary, before we can trace the relationships of different genera widely 
VOL. XI.—no. 11. 
