640 C. CLIFFORD DOBELL. 



ring them into the boiled rectal contents of a normal frog, 

 but without success. I have not been able to obtain sufficient 

 material for more extended experiments in this direction. 



The final result then is death ; and with this I finish my 

 description of degenerative changes in Opalina ranarum 

 so far as I have observed them. Before leaving the subject, 

 however, I must draw attention to the extraordinary parallel 

 which exists between these changes and certain so-called 

 "sexual" processes. In many Protozoa gamete nuclei are 

 formed from the original compound nuclei by resynthesis 

 from chromidia, very much in the same way as the solid 

 chromatin nuclei which I have just described in Opalina. 

 In certain autogamic processes the nuclei ai'e formed and 

 fuse in the same cell. Compare, for example, the autogamy 

 of Bo do lacertEe, Grassi, as described by Prowazek. The 

 animal encysts, and inside the cyst the nucleus gives oif 

 chromidia into the cytoplasm. From these chromidia a new 

 nucleus is built up, and this divides into two. Each daughter 

 nucleus forms two " polar bodies," and the reduced nuclei 

 (the gamete nuclei) approach one another and fuse. In 

 Bodo lacertte heterogamy also occurs, but in Tricho- 

 mastix lacei'tte, Blochmann, and in Entamoeba coli, 

 Losch, only autogamy is known — no other " sexual " act. 



It is possible that the process which I have just described 

 in Opalina is a kind of autogamic attempt on the part of 

 the organism to reconstitute itself. But I believe that the 

 sole explanation of this curious set of changes is to be sought 

 in the alteration in chemical and physical properties which 

 living protoplasm undergoes in dying. 



In conclusion, mention may be made of certain other 

 observations which have been made on degeneration in other 

 Protozoa. But little atteutiou has been bestowed upon the 

 matter, although in a few species degenerative changes have 

 been studied in considerable detail. Among these I may 

 name Actinospha)rium (Hertwig), Amoeba (PrandtiJ, 

 Paramoecium (Maupas, Calkins, etc.), Trichospha^riuui 

 (Schaudinn), and the sporont of Cyclospora caryolytica 



