hydrozoa. 
Ccel. 11 
From an analysis of the skeleton of Ilydraciinia ecTiinata^ of a new 
species with calcareous skeleton, and of some tertiary and cretaceous 
species, and a comparison of these structures with that of the fossil 
forms known as ParJceria, Loftusia^ Stromatopoj'a, and a species from 
the chalk described as Dradya tergcstina, Stacho, Carter (2) arrives at 
the result that “ all this chain of evidence seems to lead to the conclu- 
sion, that the whole of these organisms, both recent and fossil, were 
species of Hydrozoa^ and neither Foraminifera nor Sponges.” 
Steganophthalmous or Phanerocarpic (Acraspedote) Medusad. 
Claus (5) has studied the structure and evolution of the so -termed “ Scy- 
phistoma ” of Ghrysaora and Aurelia. In the “ Morula ’’-stage the embryo 
is formed of a single cell-layer ; the endoderm of the “ Gastrula ” is formed 
through invagination from one of the poles, but this orifice is again com- 
pletely closed and only re-opened afterwards, through the formation of the 
true mouth at a later stage, at the same place, after the fixation of the 
“ Planula ’’-larva by the broader (hitherto anterior) extremity. The 
attached portion is little by little drawn out into a stem-like foot, which 
secretes cuticular layers, forming a horny tube analogous to that of other 
fixed Hydrozoa. After the appearance of the first two (not absolutely 
contemporaneous) tentacles, two others will appear, forming the four 
tentacles of the first order ; “ EpUyrce ” or Medusae with abnormal 
(diminished or enlarged) number of radii may be referred to irregu- 
larities (retardations or accelerations) in the development of the ten- 
tacles of the “nurse.” In the direction of the four tentacles of the second 
order, four muscular strings are developed (analogous to those of Lucer. 
narice?)^ and four folds or ribs, projecting into the gastral cavity. 
Between the endoderm and ectoderm a fluid mesodermal-layer is interposed, 
corresponding to the gelatinous layer of Medusae^ and only exceptionally 
taking the character of a “ hyaline lamella it is also present in the gastral 
protuberances, which are not radial vessels ; a circular canal does not 
exist. Cnidoblasts are present in great number also in the endoderm. 
During the transformation of the Scyphistoma into a column of “ Ephyrce ” 
(Strohila), the gastral ribs — by means of which and of the stomachal 
tube the young Acalephs are kept temporarily together— correspond 
with the four primary ventral filaments of the This 
therefore has four secondary radii, corresponding with the filaments 
and the genital sacs ; four primary radii, corresponding with the four 
angles of the buccal cross and the four arms, and eight intermediary 
radii, answering to the eight primary marginal tentacles and the simple 
not ramified, radial vessels. The author maintains that the transforma- 
tion of the Acaleph-nurse into the so-termed “ Strobila ” is a true trans- 
versal division, not a masked gemmation ; but here more details would 
appear requisite before doing away with the observations of authors who 
have upheld the latter view. 
Claus has further {1. c.) studied the evolution and structure of Aurelia, 
CJirysaora, and Rhizostoma. The four so-termed “genital sacs” of 
Aurelia (wanting in Pelagidm and Rhizostomidce, being replaced by the 
