‘ 
‘uly 10, 1873] 
ON THE ORIGIN AND METAMORPHOSES OF 
INSECTS * 
VIII. 
FoR the next descending stage we must, I think, look 
: among the Infusoria, through some such genus as 
_Cheetonotus or Ichthydium. Other forms of the Rota- 
toria, such for instance as Rattulus, and still more the 
very remarkable form discovered last year by Mr. Hud- 
son,t and described under the name of Pedalion mira, 
Pian 
PLATE 5. 
6—9, Protamyxa Aurautiaca. Haeckel, 
Plate 5.—Figs. r—5, Protamceba. 
1c—18, Magosphcera planula 
Beit. zur. Monog. der Moneren, Pl. 1. 
Haeckel lc., P.l. 5. 
seem to lead to the Crustacea through the Nauplius form. 
Dr. Cobbold tells me that he regards the Gordii as the 
lowest of the Scolecida ; Mr. E. Ray Lankester considers 
some of the Turbellaria, such genera for instance as 
Mesostomum, Vortex, &c., to be the lowest of existing 
worms ; that is to say, if we exclude the parasitic groups. 
Haeckel also regards the Turbellaria as forming the 
nearest approach to the Infusoria. The true worms 
seem, however, to constitute a separate branch of the 
animal kingdom, 
We may take the genus Prorhynchus,§ for instance, as 
* Continued trom p, 167. 
t “Ona New Rotifer.” Monthly Microscopical Fournal, Sept. 1871. 
1 Generale Morphologie. _V. ii, p, Ixxix 
§ Gegenbaur. Grund. d. Vergleich. Anat. p. 2to. See also Beitrage 
Zur Naturg. der, Turbellarien. Dr. M. S. Schultze, 1851. Pl. vi, fig. r. 
207 
ar. illustration of such a low type (Fig. 59), which consists 
of a hollow cylindrical body 1 to 2”’ long, containing a 
straight simple tube, the digestive organ. 
But however simple such creatures as these may be, there 
are others which are far less complex, far less differen- 
tiated ; which therefore on Mr. Darwin’s principles may 
be considered still more closely to represent the primzeval 
ancestor from which these more highly developed types 
have been derived, and which, in spite of their great 
antiquity, in spite of, or perhaps in consequence of their 
simplicity, still maintain themselves almost unaltered. 
Thus the form which Haeckel has described * under the 
name of Protameba primitiva, Pl. 5, Fig. 1—5, con- 
sists of an entirely homogeneous and structureless 
substance, which continually alters its form ; putting out, 
and drawing in again, more or less elongated processes, 
and creeping about like a true Amceba, from which, how- 
ever, Protamceba differs in the absence of a nucleus. It 
seems impossible to imagine anything simpler ; indeed, as 
described, it appears to be an illustration of properties 
without structure. It takes intoitself any suitable particle 
with which it comes in contact, absorbs that which is 
nutritious, and rejects the rest. From time to time a 
constriction appears at the centre (Pl. 5, Fig. 2), the form 
approximates more and more to that of an hour-glass 
(Pl. 5, Fig. 3), and at length the two halves separate, and 
each commences an independent existence (Pl. 5, Fig. 5). 
In the true Amcebas, on the contrary, we find a 
differentiation between the exterior and the interior : the 
body being more or less distinctly divisible into an outer 
layer and an inner parenchym, In the Amcebas, as in 
Protamoeba, multiplication takes place by self-division, 
and nothing corresponding to sexual reproduction has 
yet been discovered. 
Somewhat more advanced, but yet of great simpli- 
city, is the Protomyxa aurantiaca, discovered by Haeckelt 
on dead shells of Spirula, where it appears as a minute 
orange speck, which shows well against the clear white 
of the Spirula. Examined with a microscope the 
speck is seen to be a spherical mass of orange-coloured, 
homogeneous, albuminous, matter, surrounded by a deli- 
cate, structureless, membrane (Pl. 5, Fig. 8). It is obvious 
from this description that these bodies closely resemble 
eggs, for which indeed Haeckel jat first mistook them. 
Gradually however the yellow sphere broke itself up into 
smaller spherules (P]. 5, Fig. 9), after which the containing 
membrane burst, and the separate spherules, losing 
their globular form, crept out as small Amcebe (PI. 5, 
Fig. 6), or amceboid bodies. These little bodies moved 
about, assimilated the minute particles of organic matter, 
with which they came in contact, and gradually increased 
in size (Pl. 5, Fig. 7) with more or less rapidity according 
to the amount of nourishment they were able to obtain. 
They threw out arms in various directions, and if 
divided each section maintained its individual existence. 
After a while their movements ceased, they contracted 
into a ball, and again secreted round themselves a clear 
structureless envelope. 
This completes their life-history as observed by 
Haeckel, who found it easy to retain them in his glasses 
in perfect health, and who watched them closely. It also 
coincides very closely with that of the Gregarinz, another 
group of singularly egg-like organisms. 
As another illustration I may take the MZagosphera 
planula, discovered by Haeckel on the coast of Norway. 
In one stage of its existence (PI. 5, Fig. 10) it is a 
minute mass of gelatinous matter, which continually alters 
its form, moves about, feeds, and in fact behaves altogether 
like the Amoeba just described. It does not however 
remain always in this condition, Aftera while it contracts 
into a spherical form (Pl. 5, Fig. 11), and secretes round 
itself a structureless envelope, which, with the nucleus, 
gives it a very close resemblance to a minute egg. 
* Monographie der Moneren, p. 43- 
+ Monographie der Moneren, p. ro, 
