1915. | J. Rrrcu1e: Hydrotds of the Indian Museum. 559 
indeed, characteristic of almost all Hydroids, but it consists of a 
single row of central thick-walled cells. Chun (1897, p. 316) says 
regarding the occurrence of such uniserial solid endoderm ‘‘ Was 
zunachst ihr Vorkommen unter den Hydroiden anbelangt, so 
fehlen sie lediglich der durch hohle Tentakel ausgezeichneten 
Gattung Hydra. Alle iibrigen Hydroidpolypen besitzen solide 
Tentakel, welche von einer einzigen Reihe derbwandiger centraler 
zellen gesttitzt werden.’’ With the exceptional case of Hydra 
must be included that of the since described Moerisza lyonsz, 
Boulenger (1908), and possibly that also of Caspionema ‘pallasi, 
Derzhavin (1912), regarding the endoderm of which the author 
makes noremark. In Hydva and Moertsta the endoderm consists 
of several longitudinal rows of thin-walled cells, penetrated by a 
fine central lumen. But in species of Tubularia which I have 
examined in detail, the lower or aboral whorl of tentacles contains 
a solid endoderm composed of many small thin-walled cells. These 
are not arranged in series but fill in irregularly the centre of the 
tentacles (see also Warren’s account of Tubularia betheris, 1908, 
p. 282). The oral tentacles of Tubularia contain the ordinary 
type of uniserial endoderm. 
The solid delicate-walled multiserial endoderm af Annulella 
bears no resemblance to the solid uniserial endoderm of the majo- 
rity of Hydroids, but closely resembles in structure and arrange- 
ment (except that there is no central cavity) the multiserial 
endoderm in the tentacles of Hydra and Moerisia, and resembles 
in a general way the solid endoderm of the aboral tentacles of 
species of Tubularia. 
BUDDING. 
The phenomena of budding in the Hydroid Zoophytes may be 
divided into three types: (I) where the bud develops on the 
parent into a miniature adult and remains attached, thus giving 
tise to colonial formation; (2) where the bud develops on the 
parent into a miniature adult which is then set free; (3) where 
the bud is set free at a simple planula-like stage and develops into 
a miniature adult away from the parent. 
(1) The colonial type of budding is exhibited by the majority 
of cnidoblastic and gymnoblastic hydroids. (2) The setting free of 
a miniature adult is much less common but is familiar through 
the example of Hydra, and occurs in a few forms such as Moerisia 
(Boulenger 1908, p.363) and Tvarella (Schulze 1876, p. 411). (3) 
The escape of a planula-like bud is an exceedingly rare mode of 
propagation, and since it is the type exhibited by Annulella calls 
for some remark. In its ultimate results it closely resembles the 
phenomena of those peculiar propagating branches of many Hy- 
droids, the separation of which—‘“‘ Scissiparité’””—has been most 
recently and ably investigated by Dr. A. Billard (1904). ‘“‘ Scissi- 
parité,’’ however, connotes the adaptation of an old structure, 
stolon or branch, to a new purpose, and can be reduced to a 
simple form of transverse fission in a portion of the hydroid 
