$ 119. 
THE HELMINTHES. 
131 
nic cells present the same successive phases as in the Cestodes and Trema- 
todes, without the appropriated vitellus undergoing any segmentation; or, 
the whole vitellus after a complete segmentation, is changed into an em- 
bryo.® 
In both cases, the embryo has the parent’s form. 
A muscular cesopha- 
gus and straight intestine appear in its body in the midst of the refuse 
vitelline granules; and thus the young animal attains its perfect state by 
simple increase and by the development of its genital organs, but without 
any metamorphosis, ” 
From the few observations hitherto made upon the development of the 
Gordiacei, it appears that the embryos exactly resemble the parents. 
1 Kélliker was the first to call the attention to 
‘these two types of development with the Nema- 
todes (Miiller’s Arch. 1843, p. 68, Taf. VI. VII.). 
With Ascaris dentata, Oxyuris ambigua, and 
Cucullanus elegans, free embryonic cells are 
formed in the vitellus without its fissuration. But 
there is a complete segmentation with Ascaris 
nigr » acuminata, osculata, 
labiata, and br data, Strongylus auricu- 
daris, dentatus, Filaria inflexo-caudata, rigida, 
and Sphaerularia bombi. After I had already 
noticed this vitelline segmentation with the Ne- 
amatodes (Burdach’s Phys, loc. cit. p. 211), which 
Bagge (Dissert. loc. cit.) described very fully, 
Kélliker (loc. cit.) attempted to reconcile it with 
the cell-theory, by regarding the cells which 
Pp in the ted, vitelline globules, as the 
embryonic cells, and in the multiplication of 
which by segmentation, the enveloping vitellus 
participates. 
2 Tt appears that, as with the Trematodes, so in 
the Nematodes, a migration of the young precedes 
their complete development. 
In the tissues of the most different insects and 
vertebrates, there are found small Nematodes 
without genital organs, and contained in a cyst. 
‘They could not get there except by a migration, 
and they cannot attain the full development of 
kind of nurse of a Dist ining peculi 
wgerm-bodies which are developed into Dzstomum. 
But the most important result obtained is that all 
Distomum are not developed by means of a cer- 
«arian, larval stage,— the economy of some making 
it ingly requisite that the devel 1 pro- 
‘cess should be more direct. — Ep. 
* (§ 119, note 2.) In regard to Trichina spi- 
ralis, the various researches upon its structure, 
made in England and America, would show that it 
is a true animal having genital organs. The fol- 
lowing are some of the references upon this sub- 
ject: Owen, London Med. Gaz. April and Decem- 
ber, 1835, or Transact. Zool. Soc. London, IV., or 
Cyclop. Anat. and Phys. Art. Entozoa; Wood, 
London Med. Gaz. May, 1835; Farre, Ibid. De- 
cember, 1835; Harrison, Report of the Brit. 
Assoc. for the Advancem. of Sc. 1835 ; Know, Edinb. 
Med. and Surg. Jour. 1836, XLVI. p. 86; Hodg- 
their genital organs or their bodies in general, 
except through a transplantation upon other ani- 
mals ; exactly as occurs with the trematodal larvae. 
(See the observations of Creplin and myself upon 
the sexless Trematodes, in Wiegmann’s Arch. 
1838, I. p. 302, 373.) 
The Trichina spiralis of man is undoubtedly an 
encysted and imperfect form of one of the Nema- 
todes, and in which one may seek in vain for gen- 
ital organs. Some of these Nematodes appear to 
increase in their cysts without their genital organs 
being developed in the same proportion. Thus, the 
Filaria piscitum are sometimes found very large, 
while their genital organs are very little developed ; 
and these last do not: probably, attain their perfect 
state, until, as with Bothriocephalus solidus, 
these worms have passed into other animals. For 
the same reason, I agree with Steenstrup (loc. cit. 
p- 118), who doubts that the Filaria piscium 
become, as Miescher has affirmed (loc. cit. p. 26), 
a globular capsule out of which there afterward 
appears an animal at first resembling a Trema- 
tode, but which finally becomes a Tetrarhyn- 
chus.* 
8 See Dujardin (Ann. d. Sc. Nat. X VIEL. loc. 
cit. Pl. VI. fig. 15, 16) upon Mermis nigrescens, 
researches which I have been able thoroughly to 
confirm.t 
kin, Lect. on Morbid Anat. of Serous and Mucous 
Membranes, I. p. 212; Curling, London Med. 
Gaz. February, 1836 ; Bowditch, Boston Med. and 
Surg. Jour. April, 1842; Luschka, Siebold and 
Kélliker’s Zeitsch. III. 1851, p. 69, Taf. III., and 
Gairdner, Edinb. Monthly Jour. of Sc. May, 
1853. The subject is one that deserves especial 
tion from Hel ists. — Ep. 
+ [§ 119, note 3.) Grube (Wiegmann’s Arch, 
fiir Naturgesch. 1849, p. 358) and Leidy (Proc. 
Acad. Sc. Philad. V 1850, p. 98) have observed 
the development of Gordius. It corresponds 
pretty closely with that of Ascaris as described by 
Bagge ; but the embryo on escaping from the egg 
is annulose and tentaculated, and differs much 
from the adult form. Nothing is known of the 
history of the animal between these two conditions. 
—Epb. 
hol 
