8364 CHARLES L. BOULENGER. 
In Mcerisia we occasionally find a lateral bud developing 
in situ; it increases in size, and forms what must be a 
modified hydranth of very irregular shape, usually with one 
or two tentacles, but without mouth or hypostome (figs. 5 
and 6, Lat. B?.). From this are developed one or more 
hydrorhizal tubes with perisarcal investment, which produce 
lateral branches; at the extremities of these ordinary 
hydranths are borne (fig. 5, Hydr.). We thus get the curious 
appearance of a small colony growing from the body of a 
hydranth. 
In some cases the lateral bud produces a hydranth without 
first forming a hydrorhiza (fig. 6). 
p. Reproduction by Transverse Fission. 
In Mcerisia we observe yet another kind of asexual 
reproduction, which may be regarded as a modification of 
the phenomenon of decapitation described in so many 
hydroids. Decapitation seems to be of frequent occurrence 
in the colonies of Mcerisia; the basal part of a hydranth 
becomes constricted off from the branch which bears it, and 
eventually falls off. Before this actually happens we can 
often notice that the branch has become considerably swollen 
below the constriction, and is on the way to becoming a new 
hydranth. This is probably repeated several times during a 
season; Dalyell (3), why first described the phenomenon, 
noticed that in Tubularia decapitation could occur as often 
as seven times in sixty-six days. 
In several colonies of M cerisia observed by me the whole 
process was being hurried over, and, even before the first 
hydranth was completely separated off, a series of constric- 
tions had appeared on the stem below it, giving rise to a 
string of more or less spherical buds (fig. 7, Strob. B.). 
These, no doubt, become detached, and develop into new 
colonies. . 
Chun (4), discussing the phenomenon of decapitation, has 
suggested that it may represent a process of very unequal, 
