1134 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [8] 



and immediately fixed them in the picro-carmine sohitiou, as given by 

 Certes/*^ with a very weak solution of osmic acid (^ per cent). The 

 Individuals which in this manner had been collected all through the 

 night were examined on the following day, but with the same result. 

 Even in these individuals no process of fission had taken place. 



These results were all the more astonishing, as invariably individuals 

 of greatly differing dimensions were found on the epidermis, which cir- 

 cumstance could be explained only by the supposition that the smallest 

 individuals had reached the epidermis from the outside. I now exam- 

 ined very carefully the bottoms of the small aquariums whi(;h had been 

 provided for the fish experimented with. The bottoms and the glass 

 walls of the aquariums were thickly covered with these infusoria, but 

 even among these 1 could not, at least by daylight, find any indications 

 of a process of reproduction by fission. The case was different, however, 

 with these infusoria after sundown. During four evenings I examined 

 the infusoria at the bottom of the aquarium with my microscope by 

 artificial light, and obtained positive results, which were the same every 

 evening. I take the liberty to give below the results of these investi- 

 gations : 



7 p. m. The infusoria became encysted on the bottom of the aqua- 

 riums. Some of these encysted forms lay entirely motionless in the 

 cyst, while others showed very distinct cilia and were observed to be 

 rotating actively (Fig. 5). Temperature of the water, 8^.5 C. [=47o.3 

 Fahr.]. 



7.45 p. m. Most of the encysted forms Avere in process of fission or 

 division ; or the fission had already taken place (Fig. 6). Ko division 

 of the nucleus could be observed; only once 1 saw a long nucleus-like 

 body lying perpendicularly to the plane of cleavage of the two indi- 

 viduals. 



8.45 p. m. The encysted individuals were segmenting into four parts 

 (Fig. 7). 



9.35 p. m. In most of the cysts eight individuals were observed, 

 which, as in the previous stages, were swimming about in the cyst in a 

 lively manner (Fig. 8). 



10.15 p. m. The process of cleavage, or fission, had progressed so far 

 that cysts with 16, 32, and even more individuals were very frequent. 



11.15 p. m. The different cysts were filled with a, large number of 

 very small active individuals. Generally after about ten minutes the 

 cyst burst, and the young infusoria were set free from it. The size of 

 these small individuals was as follows : Long diameter 0.0816, and 

 short diameter 0.0612 millimeter. Temperature of the water, 8.5 de- 

 grees 0. 



In Fig. 9 I give an illustration of this last stage of thcMr development, 

 which closely resembles the so-called "Morula" stage of the Metazoa, 

 the figure being drawn from a picro-carraine preparation. 



leCertes, p. 435. 



