240 FEESH-WATEE EHIZOPODS OF NOETH AMEEICA. 



instance of segmentation, as represented in figs. 11-22, but differing in the 

 earlier steps from 'anything of the kind I had previously or since have seen. 



At first, the Aetinophrys appeared as a pair of ordinary individuals, 

 retaining between them a third spherical ball nearly as large, as seen in fig. 

 11. The nature of this intervening ball I did not discover, but conjectured 

 that it was a third individual of Aetinophrys, altered from the usual con- 

 dition. It was granular, without vacuoles and rays, darker on one side 

 than the other, and with a central clearer spot, probably indicating the 

 presence of a nucleus. 



Three hours subsequently the pair of Actinophry es remained essentially 

 unchanged, but were united by a cylindrical isthmus, which contained the 

 third ball reduced to little more than half its original size, and with a less 

 distinct outline,* as represented in fig. 12. 



Two hours later the two Actinophryes remained unchanged, but the 

 isthmus had become rather longer and narrower. The intervening ball had 

 melted away, leaving in the isthmus, besides diffused granular matter, a 

 large clear nucleus and a group of fat globules. See fig. 13. 



Soon after, the two Actinophryes remaining unchanged, excepting a 

 slight flattening at the opposite poles, the isthmus became narrowed on the 

 left and retained the nucleus and oil globules on its right, as seen in fig 14. 



At the next step, the two Actinophryes increased in diameter in a 

 direction opposite to that transverse with the isthmus, and became sunken 

 at the opposite poles, as seen in fig. 15. 



The isthmus continued to become narrower until it formed a mere 

 cord, and the nucleus, together with the oil globules, were drawn into the 

 Aetinophrys on the right, as seen in fig. 16. 



About 9 o'clock the isthmus parted, and the two Actinophryes appeared 

 as represented in fig. 17: the individual on the right being cordiform; that 

 on the left reniform. Later, the reniform individual, or that on the left, 

 assumed a dumb-bell form, fig. 18^ its isthmus then gradually narrowed and 

 elongated, fig. 19, and finally parted into two individuals. The cordiform 

 Aetinophrys, or the individual on the right (fig. 17), produced in the divi- 

 sion of the original pair, contracted at the point, so that it became reniform, 

 as seen in fig. 20. This now, still retaining the apparent nucleus and oil 

 globules of the above described granular ball, also assumed a dvimb-bell 



* The outline has been made too dark in the lithograph ; in the original drawing there is none. 



