110 Miscellaneous. 
by the employment of this experimental process; for the ovum of 
the Ascidians is surrounded, outside its vitelline membrane, by a 
cellular envelope, the elements of which may be mistaken (as indee 
has been done) for cells of the mulberry-like mass which is the 
result of segmentation. But when we first of all study the iere 
envelope, we can no longer have any doubt as to the nature of the 
4 The results of artificial fecundations are easily obtained ; and with 
their aid we may with certainty trace, starting from the segmenta- 
tion, the «leere of the first form of the embryo, its exclusion, 
and the transformations which lead up to the perfect animal. 
ere is not a naturalist who has observed the embryos of the 
Asidians and En not expressed the astonishment produced in him 
by the sight of these tadpoles, so active at first, and finally getting 
rid of their tail or locomotive organ, fixing themselves and becoming 
sedentary. 
Now, from this point of view, Molgula presents a very remarkable 
exception. Long before hatching, the tadpole-like embryo of the 
Phailusie moves within the she : which encloses it, and turns about 
rking movements. The embryo of Molgu la, on the contrary, 
with jer ry 
moves slowly, and its vcrc are but slightly perceptible beneath ` 
e cellular envelope which covers it. Nevertheless its movements 
through which it issues like an Ameba, by flowing like a rounded, 
plastic, fluid, pasty mass, destitute of a tail, and remaining sedentary 
at Aisles of the vessel, 
times I repeated this observation in the fear that I might 
Rare um abnormally formed embryos for properly constructed 
indi D^ s; and the results were always the same. 
m this time, therefore, it is ascertained that the body of the 
jim Mağa is supple and contractile, modifies its form mid y 
amæboid movements, but never enjoys that agility or activity which 
so remarkable in the first movements of the life of the other grise 
whose embryogeny has been studied. 
ost immediately after exclusion, the young Molgula presents, 
in its globular body, zones, the different nature of which is shown 
by different tints. à One of these, the outermost, produces some pro- 
natural fecundations, and seen them quickly attach themselves. 
The ease with which they may be kept alive enabled me to follow 
