Mr. H. J. Carter on the Spermatology of a new species o/Nais. 99 



luckily the watch-glass containing it was upset, and thus the 

 means of proving it to be so, by their further development, lost. 



Abnormal Development of the Yelk. 



If the yelk become abortive, fissuration does not appear to 

 take place, but several sacs containing a fine granular matter are 

 developed in the midst of its substance (fig. 45), while gradually 

 this fine granular matter becomes transformed into globular 

 cells, each of which contains a yellowish refractive oil-globule, 

 if it be not a nucleus (a, a). As this is taking place, the sacs, 

 which are now plastic and endowed with motor power, put forth 

 respectively a tubular prolongation, which, on reaching the shell 

 of the ovum, becomes suddenly diminished in calibre, and thus 

 passes through it in an attenuated form (a, a) ; or the sac may 

 assume nothing but a tubular form from the first, and, after 

 penetrating the shell, expand into a globular or conical shape, 

 ending in a narrow papillary eminence (d). Finally, the ex- 

 tremity of the tube, in both forms, yields to the pressure of the 

 internal contents, which now rapidly issue, one after another (b), 

 in the form of monociliated monads, about 1 -5600th of an inch 

 in diameter (46«). These, after swimming about for a short 

 time, become fixed, and the next day may be observed to have 

 lost their cilium and to have put forth a short tube (b), after 

 the manner of the parent sac ; but whether this ends in another 

 division of their contents into still smaller monads, or they thus 

 perish, I am ignorant. 



This development of the yelk, which does not occur if it be- 

 come putrescent, is but another instance of what I have shown 

 to take place in the protoplasm of the spores, &c, of Algse*, 

 when arrested in its progress to assume the likeness of the plant 

 from which the spore has been produced ; that is to say, that 

 instead of doing this in either instance, the contents of the ovum 

 and the spore respectively become transformed into monads, and 

 finally into rhizopodous cells — that is, reduced to the lowest 

 form of organic life with which we are acquainted. 



I have stated that the sacs in the yelk "put forth tubular 

 prolongations;" and this is done in the following way (if I may 

 judge from similar sacs putting forth similar tubes under similar 

 circumstances in the algal cell) : viz. the endoplasm or protoplasm, 

 whichever term is adopted, appears to be compelled to obey a 

 law by which its surface becomes covered with a pellicle, and 

 this pellicle again compelled by another law to harden soon 

 after it has been formed; thus circumstanced, the endoplasm 

 carries a pellicle with it, that corresponds in every way to its 



* Annals, vol. i. 3 ser. p. 35, &c. pi. 3. figs. 13-15, and vols. xvii. & xix. 



