830 Mr. W. C. Minor on Natural and Artificial Section 



The following summary will illustrate this. In Stylaria longiseta, 

 one example (April 16) was reduced to 10 rings, grew out but 

 little, and divided between the 12-1 3th. When again reduced 

 to 10 rings, it grew out much longer, but renewed fission at 

 the same point as before. It was then reduced to 11 rings, and, 

 growing out, again divided between the 12-1 3th. One of its 

 buds (May 14) began fission between the 15-16th, was reduced 

 to 12 rings, then grew out and recommenced fission between the 

 14-15th, and was being reduced again when lost. In another 

 case, the Naid was reduced to 12, grew out and renewed fission 

 at the 14-1 5th, was again reduced to 12, and, growing out again, 

 renewed fission at the same point. It was a third time reduced 

 to 12, and growing out again a third time, renewed fission be- 

 tween the 14-15th hook-combs. It was then reduced to 11, 

 when very unfortunately it was lost. In Nais rivulosa, an example 

 that had been giving off buds just back of the 19th ring, in- 

 creased to something like 33, and then again renewed fission 

 between the 19- 20th. Another example, that had given ofi" 

 buds at the 15th, grew out to over 35, and then renewed fission 

 at the 15-1 6th. After two or three buds had been given oif, it 

 again elongated, and then renewed fission between the 20-2 1st 

 hook combs. 



Now, while in Stylaria the " renewal of fission " appears to 

 difier from the commencement of fission, with which I believe 

 it is essentially homologous (except by not occurring as far back), 

 which may be owing to the want of fuller observation, and while 

 in this genus it might be supposed to be merely a means of 

 continuing the process of " parting," which must otherwise soon 

 cease, we find that it occurs in Nais rivulosa without any change 

 of the point of budding, without any apparent necessity, without 

 performing the very function that we might judge from Stylaria 

 was its peculiarity. And what is more, it also occurs in Nais 

 rivulosa for the performance of this very function. This fact 

 suggests something more than a physiological meaning in the 

 ''renewal of fission." While the phenomena connected with it 

 seem to show that the distinction between this, the " renewal of 

 fission," and other forms of fission is more than a difference of 

 function, I am far from claiming that there is any fundamental 

 difference, like that between metagenetic and monogenetic fis- 

 sions. I may add that I have not been able to discover that the 

 point of its occurrence bears any relation to the number of buds 

 already given off*. 



The sum of the preceding observations tends to show that the 

 " renewal of fission " has some special characters that suggest a 



* There are some other differences to be considered in a future paper 

 upon the histological nature of fission, 



