234 
ALFRED GIARD. 
difficulty, it may be noted, is found with regard to the buds 
of the sporocysts of the Trematoda, and all zoologists who 
have occupied themselves with the study of these animals 
know how difficult it is to demonstrate the cells which form 
the bud-like embryo of a Bucephalus or of any Distoma. 
Occasionally the primary buds produce secondary buds. 
When these buds have arrived at a certain size, they are 
composed clearly enough by a single layer of cells, which 
then proceed later to form an internal layer by delamination. 
It appears, from what has been just stated, that the 
endoderm alone of the parent animal enters into the forma- 
tion of the bud-like embryos, but it must not be forgotten 
that the papilliferous ring, or that which represents it in 
Bitoshia, is characterised by great opacity, and that it is 
possible that at certain points ectodermal cells penetrate to 
the interior of the endodermal sac. 
With their increasing development, the sporocysts lose 
their original form and become very voluminous. Often 
there are found several sporocysts in the interior of a spe- 
cimen of an Ophiurid. This very active gernmiparous 
reproduction of the Orthonectida explains how it is that 
these animals are found in such great abundance in the 
Echinoderms infested by them. The phenomenon is one 
very similar to that occurring in the case of the Dicyemida ; 
but with regard to these latter, it is almost impossible to 
find a Cephalopod which does not swarm with them, whilst 
the Orthonectida are comparatively rare. 
VI. — Oviparous Eeproduction. 
Side by side with the sporocysts just described, we find 
in the infested Ophiurids a great number of cellular masses, 
which must be considered as eggs in various stages of seg- 
mentation. 
In the case of Bhopalura, I have only been able to 
observe a small number of these embryonic stages (PI. 
XXII, figs. 19, 20, 21). The little which 1 have been able 
to observe leads me to the conclusion that the segmentation 
is irregular, and that the planula is formed by epibole, as in 
the Dicyemida. Each division of the cells in the mulberry 
mass gives rise to stellate figures, so well known at the 
present day by the name of caryolitic figures or amphiasters. 
The use of osmic acid enables one to observe them with the 
greatest facility. 
In the study of the development of Intoshia I have been 
more successful. Here the segmented egg forms at first a 
perfectly regular blastula, the cells of which are at first 
