OF THE ROTATORIA. 451 



iial vesicle may, by repeated fission, resolve itself into numerous clear vesicles, 

 without any further change, except that of an attendant grouping of the yelk- 

 particles about the products from the germinal vesicle, or that perhaps the 

 winter eggs, at theii' origin in the ovary, enclose a number of nuclei (germinal 

 vesicles) unlike other ova, which never commence with more than one nucleus 

 (germinal vesicle). If," continues Leydig, " I rightly understand Huxley, 

 this is the manner of development of the winter eggs of Lacinularia socialis ; 

 and the bisection into two equal halves, which I formerly referred to fission, 

 has, according to this writer, no relation to it." 



Respecting this description. Prof. Huxley remarks that he thinks Leydig 

 " has not observed the genesis of the ephippial ova with sufficient care, and 

 he thence interprets theii' stnictui'e by supposing that they are ordinarily 

 fecundated ova, which have undergone a peculiar method of cleavage ;" and 

 having quoted the opinion of other naturalists, he goes on to say — " it will be 

 observed that all these authors consider the ranter or ephippial ova and the 

 ordinary ova to be essentially identical, only that the former have an outer 

 case. The tmth is, that they are essentially different stnictiu'es. The true 

 ova are single cells which have undergone a special development ; the ephip- 

 pial ova are aggregations of cells (in fact, larger or smaller portions — some- 

 times the whole of the ovary) which become enveloped in a shell and simulate 

 true ova. 



" In a fully-groTVTi Lacinularia which has produced ova, the ovary or a 

 large portion of it begins to assume a blackish tint (XXXYII. 22) : the cells, 

 with theii' nuclei, undergo no change ; but a deposit of strongly- refracting 

 elementary granules takes place in the pale connecting substance. Every 

 transition may be traced, from deep-black portions to unaltel'ed spots of the 

 ovarium ; and pressure always renders the cells, with their nuclei, visible 

 among the granules. The investing membrane of the ovary becomes sepa- 

 rated fi'om the dark mass, so as to leave a space (XXXYII. 24) ; and the 

 outer sui'face of the mass invests itself with a thick reddish membrane, which 

 is tough, elastic, and reticulated from the presence of many minute apertures. 

 This membrane is soluble in both hot nitric acid and caustic potassa. 



" The nuclei and cells, or rather the clear spaces indicating them, are still 

 visible upon pressure, and may be readily seen by bursting the outer coat. 



" By degrees the ephippial ovum becomes lighter, until at last its colour is 

 reddish -brown, like that of the ordinary ova ; but its contents are now seen to 

 be divided into two masses, hemispherical from mutual contact (XXXVII. 

 21). If this body be now crushed, it will be found that an inner, structure- 

 less membrane exists within the fenestrated membrane, and sends a partition 

 inwards, at the line of demarcation of the two masses. The contents are 

 precisely the same as before, viz. nuclei and elementary granules. This, 

 indeed, may be seen thi^ough the shell without crushing the case. 



" I was unable to trace the development of these ephippial ova any further. 

 Those of Notoynmata, it appears, lasted for some months without change (Dal- 

 rymple). 



" It is remarkable that in Lacinularia these bodies eventually, like the 

 ephippium of Daphnia, contain two o^nim-like masses ; and there can, I think, 

 be Uttle doubt that the former, like the latter, are subservient to reproduction. 



"There are two kinds of reproductive bodies in Lacinularia : — 1. Bodies 

 which resemble true ova in their origin and subsequent development, and 

 which possess only a single vitellary membrane. 2. Bodies half as large again 

 as the foregoing, which resemble the ephippium of Daphnia, like it having 

 altogether three investments, and which do not resemble true ova, either in 

 theu' origin or subsequent development ; which, therefore,- probablv do not 



2g 2^ 



