OF THE PROTOZOA. GEEGAEINIDA. 



Stein stated that, on the completion of the act of apposition, an actual 

 fusion of the contents of the two animals transpired, the opposed walls being 

 previously removed by absorption. Other observers state, however, that there 

 is no such removal of the external membranes, and that the reproductive 

 processes in the interior of each being proceed without any real commingling 

 of their contents, which is a subsequent and probably not a necessary 

 event. 



This act, which, fi'om its general resemblance to the zygosis of plants, is 

 spoken of as one of conjugation, appears immediately concerned in the de- 

 velopment of a multitude of germs "svithin each Gregcunna, by the general 

 breaking up of the granular contents. Still, if Lieberkiihn's account be ad- 

 mitted, this process of conjugation is not a necessary prelude to the develop- 

 ment of the internal germs ; for, according to it, this result may accrue in 

 individuals which have never conjugated. 



The germs assume a rod- or spindle-shaped figure, which, from its re- 

 semblance to the prevailing form of the Naviculce, has suggested for them the 

 name of " J^avicellce " or " pseudo-Navicellce.^^ They consist of an external 

 comparatively firm wall, enclosing a finely-granular gelatinous substance. 



When the *' Navicellce " are sufficiently matui^e, the cyst of the Gregarince 

 biu'sts and sets them at large. Their future history, according to Lieberkiihn's 

 researches, is, that the case of each jpseiido-Navicella ruptures and gives exit 

 to the soft contained matter, which at fii'st much resembles a minute Amoeba, 

 but gradually assumes, by progressive growth and the formation of a pellicle 

 around it, the characters of a Gregarina. 



Between this mode of development of Gregarinida and that of the Ciliated 

 Protozoa, Leuckart draws this distinction, that in the former it consists in 

 the production of granular germs, in the latter of living embryos. But it may 

 be questioned whether there is a positive difference in kind between these 

 two results of the reproductive process, and whether, on the contrary, the 

 Navicellce of the Gregarinida may not be considered as merely encysted em- 

 bryos, homologous with those of Colpoda Cucidliis among the CiLiata. 



The act of conjugation in the Gregarinida is not precisely like that occui'- 

 ring among the lower Algae, the leading difference being that in the former 

 there is no commixture of the two approximated beings. In all essentials, 

 indeed, conjugation in this family resembles that believed to happen in the 

 Actinophryina. 



There has been much dispute whether the Gregarinida are to be held in- 

 dependent animals, or merely embryonic phases of others ; the balance of 

 authority is in favour of the former view. Kolliker and Leydig advocated 

 the opinion that they are metamorphic stages of Anguillulce or Filarice, or a 

 link in the series of development of the Helminthidce. The arguments adduced 

 by Leydig are thus briefly stated (J. M. S. i. p. 208, and Miiller's Archiv, 

 1851) : — " In the intestine of a large species of TereheUa he was enabled to 

 observe the most distinct transition between Filaria-like Nematoid wonns and 

 Gregarince. The forms of the latter, which he observed not once only, but 

 many times, were — 1. A Gregarina of from 0-02'" to 0'04'" long, which had 

 the form of an elongated sac, rounded at one extremity, and sharp at the 

 other. The contents were those usual in the Gregarince — a consistent fluid 

 with a corpuscular substance, which did not occupy the pointed end, and im- 

 bedded in this a clear vesicle -^ith a nucleus. 2. A Gregaiiniform creature, 

 of a spindle-shaped figure, closely resembling Gregarina Terehellce, Kohh 

 3. A Gregarina, generally resembling the preceding, differing only in two 

 particulars : the internal substance is arranged in longitudinal streaks ^ 

 and the body, instead of being straight, is more or less curved at each end. 



