q2 THE ACALEPHAE. $ 70. 
of procreation, the females of some Discophora are easily distinguished 
from the males by the numerous pouches of their tentacles, and in which 
eggs and newly-hatched young are carried for a short time,™ 
§ 70. 
As yet, the development of a few only of the Acalephae has been traced. 
It is attended by a remarkable metamorphosis. 
After the usual segmentation of the vitellus, ovoid embryos resembling 
infusoria are developed; these turn freely on their axis, and swim about in 
the water by means of ciliated epithelium. Shortly after, they become 
attached by the anterior extremity to some object. Upon the opposite free 
extremity tentacles appear, and between them the mouth. The animal has 
then the form of a Polyp. It is during this period that the young ani- 
mal reproduces by gemmation,® and sometimes by transverse fissuration. 
This last mode occurs in the following remarkable manner : 
The polyp-like animal increases in length, and its body divides trans- 
versely into many segments. 
Around each of these segments eight bifid 
processes are developed; after this, each segment is successively separated 
from before to behind, and they float about for a time as eight-rayed Aca- 
Jephae, but soon attain, however, their adult condition.” 
seen fenital organs of the same form between the 
tentacles of Agalmopsis ; but he found at the same 
time (loc. cit. p.38, 43), in the campanuliform individ- 
uals produced from buds, testicles with Agalmopsis, 
and ovaries with Diphyes. It may therefore be 
justly supposed that these various Siphonophora 
are compound, sexless individuals, which, like the 
Hydrina and Sertularina, reproduce by alternation 
of generation,—that is, by buds, — individuals 
shaving sex. 
12 Medusa aurita and Cyanea capillata; see 
Ehrenberg, Abhandl. &c. loc. cit. Taf. III. fig. 1, 
2, Taf. VIII. fig. 1; also, Sars in Wiegmann’s 
Arch. 1841, I. p. 19. 
1 The development and metamorphosis of Me- 
dusa aurita and of Cyanea capillata have been 
observed by Siebold (Beitrage loc. cit. p. 21, Taf. 
I. II. ; and Froriep’s neue Not. No. 166, 1838, p. 
177); and by Sars (Wiegmann’s Arch. 1841, I. p. 
19, Taf. I.-IV.). In the first stage of development. 
(see Ehrenberg, Abhandl. &c. loc. cit. Taf. VIIL. 
fig. 15-18 ; also, Stebold, Beitrage loc. cit. Taf. I. 
fig. 17-19; and Sars, Wiegmann’s Arch. loc. cit. 
Taf. I. fig. 1-6), these infusoria-like Medusae have 
deen regarded by Baer as the larve (Meckel’s 
Deutsches Arch. VIII. 1823, p. 389). 
2 Siebold, Beitrage loc. cit. p. 29, Taf. I. fig. 
25-33, Taf. Il. fig. 34; and Sars, Wiegmann’s 
Arch. loc. cit. Taf. I. fig. 7-31. During my last 
visit at Trieste (autumn of 1847), I convinced 
myself that the young of Cephea Wagneri are 
developed wholly like those of Medusae, by passing 
from infusoria-like forms to polypoid young ani- 
mais.* 
8 The reproduction of the polyp-form Medusae 
‘by buds has been observed by Sars in Cyanea 
* (§ 70, note 2.) See, also, for recent researches 
on the development of Cephea, Ecker, Bericht tib. 
die Verhandl. d. naturf. Gesellsch. in Basel. VIII. 
1849, p. 51; Busch, Beobachtungen ub. die Anat. 
&c. Berlin, 1851, p. 30; and Frantzius, in Sie- 
aanilata 
He has also seen them develop pedi- 
* cies .rum the end of which new individuals would 
appear, which resembled Polyps. See Wiegmann’s 
Arch. Joc. cit. p. 26, Taf. I. fig. 37, 41, 42, 38, 39, 40. 
4 These young Medusae, whilst composed of rings, 
have been taken for a new genus (Scyphistoma) of 
Polyps by Sars (Isis. 1833, p. 222, Taf. X. fig. 2). 
Steenstrup (Ueber d. Generationswechsel, p. 17) 
has regarded them as nurses of the Medusae. At 
a latter period, when the rings have been separated. 
and have acquired the bifid prolongations, Sars 
(Isis. 1833, p. 224, Taf. X. fig. 4; and Beskrivei- 
ser, &c., p. 16, Pl. III.) has described them as a 
new species. of Medusae (Strobila octoradiata). 
But lately he has perceived that they are the young 
of Medusa aurita (Wiegmann’s Arch. 1837, I. 
p. 406) ; it did not occur to him, however, that these 
young constitute, very probably, the genus Ephyra 
of Eschscholtz (see Wiezmann’s Arch. 1841, Th. 
I. p. 10). It will probably be discovered that 
many small campanulate or discoid Medusae 
are only the young of other Acalephae; for it is very 
likely that they all undergo a similar metamorpho- 
sis. It may also prove that many naked Polyps 
are only transitionary forms of known species of 
A ye In this ion the observation of 
Dujardin (Comp. rend. 1843, p. 1182) deserves 
the attention of naturalists. In tracing the devel- 
opment of on of the Discophora allied to O. i 
he observed that vhis animal in its early condition 
separated from a corallum resembling that of Syn- 
coryne, and was of a form quite like an Eleuthe- 
ria. However various these developing forms may 
be, that one must be regarded as the real one 
which exists during the development of the testi- 
cles and ovaries.f 
bold and Kélliker’s Zeitsch. f. Zool. IV. p. 118, 
June, 1852.— Ep. 
+ [§ 70, note 4.) In regard to the development 
of the Acalephae, it may be d that recent 
researches, few as they are, have verified some 
