RECENT MEMOIRS ON FRESHWATER RHIZOPODA. 333 



sometimes elliptic, or with a concavity at one side, of a pale 

 blue colour and refractive ; they are the germs or germinal 

 bodies. Slight movements of these are noticeable, consisting 

 of turnings on the longitudinal axis (fig. 3). 



The further development of these germs becomes first 

 rendered evident by the appearance of a minute, pale rose- 

 coloured refractive spot at both poles, the first vacuole, which, 

 even to the final development of the form, but seldom 

 collapses. In order to distinguish these from the subsequent 

 larger contractile vacuoles the author gives them the name 

 of " stigma " ; he hence names the first state of the de- 

 velopment the monostigma-form (fig. 4). He was long in 

 doubt as to the subsequent mode of development, until he 

 saw two " germs " become mutually fused (fig. 4); they lie 

 alongside, a process from one seems to pass into a depression 

 in the other, a fusion ultimately takes place by the two op- 

 posite poles at one end — the conjugation poles — (without ex- 

 ception the larger and greater in mass), becoming inosculated, 

 the other poles remaining with stigma persistent, named the 

 stigma-poles, and remaining as distinct lobes of conical form 

 with an intervening narrow sinus. The product of this 

 zygosis is the second state of the development of the germ, 

 and represents the diplostigma-form (fig. 5). These are non- 

 nucleated protoplasmic masses ; with this partial fusion a 

 new activity is imparted -, a single one would seem not ca- 

 pable to grow into the final form — a new Troglodytes. 



The first indication of the origin of a nucleus coin- 

 cides with a grouping of the increasing granules, which 

 at first generally distributed, by degrees become more massed 

 in the middle zone ; soon thereupon a separation of the 

 cluster of granules ensues, leaving a median contourless 

 whitish spot, the optical expression for a fluid-drop ; this now 

 becomes circumscribed by a delicate line, and the same time 

 retreats backwards from the stigma-pole (fig. 6). Simul- 

 taneously with the commencement of change of place of 

 the probably still thick-fluid nucleus, a further alteration 

 of the grouping of the granules takes place gradually, 

 collecting towards the middle, and by degrees, in fact, 

 forming the " girdle ;" the nucleus, arrived at its normal 

 place, becomes by degrees consolidated, its nucleolus recog- 

 nisable, and its development finished. 



The narrow sinus separating the lobes of the conjugated 

 body by degrees disappears, their boundary becomes the limit 

 of the oral zone of the young Troglodytes ; the stigmata 

 seem to remain whilst the pulsating vacuoles make their ap- 

 pearance in their place just behind the median granular zone. 



