94 ME. LUBBOCK’S ACCOUNT OF THE TWO :METH0DS OF EEPEODUCTIOK 
the whole process appears strictly comparable to the facts which have been observed in 
Monostoma mutabile. 
In the sac above-mentioned is contained the embryo Dajjhnia, in which already, when 
the vitelline membrane is cast, most of the futui’e limbs may be discerned. The carapace 
covers as yet only half of the body, and appears to be attached to it by the whole inner 
surface. The large antennae also attain about the same length, and are folded down close 
to the body; their basal portion and two three-jointed branches can be distinguished, and 
the terminal setae soon afterwards make their appearance. The small black eye also can 
now be seen, but the large compound eye, which at first consists of two dark spots which 
gradually coalesce, does not arise till later. The large upper lip is situated between the 
two large antennae, and immediately behind it are the mandibles, which, seen from the 
side, appear like pears attached by their small ends, but from below appear as hemisphe- 
rical bosses. Behind the mandibles are the first pafr of maxillae, and behind these again 
I believe myself to have seen the second pair of maxillae, as Zaddach describes them'^: 
but of this I do not feel quite certain. The head is separated from the body by a con- 
striction at the back. 
The five pairs of branchial legs form a distinct and separate series, and may about this 
time be distinguished, arising apparently as folds of the blastodermic membrane. The 
limbs and outer part of the body at this time consist of a cellular substance, while the 
centre is occupied by the yolk-masses, and generally a few free oil-globules. 
In Daphnia therefore, as in Crustacea generally, the appendages make then’ appearance 
before the body is divided into segments. 
The earlier naturalists who have written about the Baphnice have asserted that all the 
young developed from any one brood of agamic eggs, are of one sex. I have never met 
with an exception to this rule, and have little doubt that it always holds good ; in one 
case, indeed, a very large brood, eighteen in number, were all males, though this sex is 
usually, and was then, much rarer than the female. 
Before quitting the subject of the agamic eggs, it will not be uninteresting to compare 
the process with that of the formation of the corresponding eggs of Aphides, as given by 
LEYDiuf, as opposed to the very different accounts of J. V. CaeusJ and Dr. Bukxetti^. 
It is evident that in Leydig’s Plate 5. A, fig. 1, 1 is homologous to the mother-cells, 
which I have in this paper called ovarian masses (c); the cells («, a) correspond to [g), and 
the enlarged one [b) to those marked [g') in my figui-es. 
Indeed, if we except the non-essential difference, that in Daphiiia the developing eggs 
do not alter their place in the ovary, the whole process, as now detailed, is so similar to 
that which is described by Leydig in the Aphides, as to confirm in a remarkable maimer 
* Ueber den Ban und Entwickelung der Gfliederthiere. 
t SiEBOLD and Kollikee’s Archiv, 1850, p. 62. 
X Zur naheren Kenntniss des Generation swechsels. 
§ Dr. Buenett “ On the Development of Viviparous Aphides,” Ann. and Mag. of Hat. Hist., Aug. 1854 
and in Silliman’s American Journal, January 1854. 
