188 Transactions of the Society. 



in fig. 5, plate V. In the middle of this, at tliis time, there was a 

 delicate line visible, parallel to its length. This became stronger 

 as the neck lengthened, as in fig. 6. Still the dividing organism 

 pulled its dividing parts away from each other, by the vigorous 

 antagonism of the flagella ; and the neck rapidly elongated, and 

 split with considerable separation of the two lines of sarcode, as 

 seen in fig. 7. But simultaneously with this there is a horizontal 

 splitting of the cord a, fig. 7, which widely separates, and when 

 the organism is seen on its dorsal aspect, shortly after this condition, 

 it reaches that shown in fig. 8, where three flagella, of double 

 length, are tightly stretched between the dividing organism, the 

 upper one on a difierent plane to the two lower ones, and by a 

 vigorous movement this is soon snapped in the middle, and two 

 organisms quite complete are severed from each other, as in figs. 9 

 and 10, plate V., and fig. 12, plate IV. 



It was impossible of course to follow both, but the one followed, 

 in every case swam, after fission, with great vigour for from two to 

 four minutes, when the first symptom of fission commenced again, 

 and on the average occupied from four to five minutes in completion, 

 from the moment when the first dorsal depression showed itself to 

 the end of the process. 



At this point the sparseness of my material greatly hampered 

 me. I w^as deeply desirous of working out the history of the form 

 to the end, while the actual material was before me. It was visibly 

 diminishing ; and although I had taken much pains to produce a 

 new crop in other vessels, by sowing this one and subjecting it to 

 the same conditions, I could have no certainty that it would 

 succeed. Fortunately I did succeed twice afterwards in getting 

 moderate quantities only ; these were obtained respectively eighteen 

 months and a little over three years subsequently. 



It was not until about a year since that I was able to steadily 

 follow the continuous fissions of three single and separate forms 

 successively, by keeping one division continuously in view to the 

 end. In one case there were forty-five and in two cases forty-two 

 fissions, and the last divided form in each case entered upon the 

 springing condition to which I have called attention. 



It is in the next stage of the development of this organism 

 that the real difficulty and the only incompleteness presented 

 itself. 



In all the monads hitherto studied, it will be remembered that 

 besides the fissional stage, there is a state of fusion on the part of 

 two individuals resulting in the production of spores : conditions no 

 doubt representing in some sense the non-fertilized and the 

 fertilized products of the micro-fungi. 



But in all the cases known, the occurrence of this fusion is 

 relatively rare. In this instance I had almost suspected that there 



