54 MCMURRICH. [VoL. III. 
by Klunzinger, and show an intermediate stage in the com- 
plication of the mesogloeal enlargements, the Bahaman forms 
representing the simplest stage; while the form mentioned by 
Klunzinger in a foot-note, the P. pzunulatum, Martens, from 
Singapore, a specimen of which is in the Berlin Museum, rep- 
resents the most complicated condition, the pinnulation being 
even more marked than in Klunzinger’s figures. 
The tentacles of the disc are small wart-like structures, whose 
structure is shown in Pl. IV., Fig. 11. Lesueur (?17) describes the 
tentacles as perforated warts; but I was not able to distinguish 
any trace of a pore inmy sections. The ectodermal muscle layer 
of the disc is not very strong, the nerve layer (z), as in the ten- 
tacles, being well marked. The ectoderm is raised into numer- 
ous elevations, as may be seen from Fig. 11, ec, the mesogloea 
not taking part in their formation. 
The mesenteries are arranged in four cycles, of which the 
first consists of 12 mesenteries, which are attached to the stomo- 
dceum throughout its full extent; the second, likewise of 12, 
has them attached only about half-way down the stomodceum ; 
while the third cycle has its 24 mesenteries entirely free and 
imperfect. The longitudinal and parieto-basilar muscles are 
present, the former being fairly well developed (Pl. IV., Fig. 9) 
and limited to the outer two-thirds of the non-reproductive 
portion of the mesentery; while the latter, its upper margin 
forming a fold upon the surface of the mesentery, is limited to 
its lower one-quarter. The inner stomata are present, but I was 
unable to determine the presence of any outer one. 
All the mesenteries, even the directives, are gonophoric, and 
the animals are bisexual. In connection with the testes I ob- 
served what seems to be a structure corresponding to the “ fila- 
mental organ,” which the Hertwigs (79) have described in 
ovaries of certain forms examined by them. From their studies 
of Adamsia (Calliactis) they were inclined to consider this pecu- 
liar organ a portion of the protoplasm of the ovary; but later, 
R. Hertwig (82) found in Corallimorphus rigidus positive proof 
of its origin from the endodermal epithelial cells in the neigh- 
borhood of the ova. I am not aware that its existence has 
hitherto been definitely described in connection with the testes, 
though what Jourdan has described (77) as occurring in the 
testes of Actznza equina is probably of this nature. Its occur- 
