522 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Polytoma of the last generation not only divide into eight and then 

 into four several times, but can also produce progeny with the capacity 

 for conjugating. 



Besides conjugation, the Polytoma have another way of reaching 

 the resting stage. In P. spicatum was observed a similar condition 

 to that which exists in Cldamydococcus. After the loss of the cilia, 

 the body-substance began to detach itself from the envelope, took the 

 spherical form and secreted a clear membrane on its surface. After 

 this no division of the cells took place, the membrane became some- 

 what thicker, but how the little ball escaped from the parent 

 envelope, and wLat became of it afterwards, could not be observed. 



Whether the Polytoma reach the resting state in one way or tho 

 other, in both cases we have globular cells. To further the trans- 

 formation of the cells to the Polytoma, the cells, after remaining long 

 in water, should either be dried and afterwards soaked in fresh water, 

 or removed direct into a rich solution of organic matter (for example 

 a 2-3 per cent, solution of gelatine in an infusion of hay). In both 

 cases the young will during the night slip out of the cells. In the 

 large cells a division into four first takes place, and in the small ones 

 into two, and then the young ones appear. A palmella or pleura- 

 coccus condition was not observed. The cycle of development of a 

 Polytoma lasts 3-14 days. 



If we compare the development of Polytoma with that of tho 

 chlamydomouads, we find at once that P. uvella cannot be called, with 

 Cohn, Chlumydomonas hyalina, and that the Polytoma are not to be 

 classed with the Chlamydomouads, although, like the latter, they 

 belong to the VolvocinesB. 



Further particulars as to the structure, the variety of division, and 

 the development of both species of Polytoma, as well as their devia- 

 tions from normal development, will shortly appear in the memoirs of 

 the Odessa ' Neurussische Naturforscher-Gesellschaft.' 



Ophryocystis BiitscMii.* — A. Schneider has discovered in the 

 Malpighian vessels of P/ctjjs a most curious new sporozoarium. It has 

 the form and external appearance of an Amoeba; its body is often 

 covered with simple or divided digitiform processes, which may equal 

 or exceed the central mass in length. The latter, which is charged 

 with granules, contains from one to ten spherical nuclei 3 yu, in 

 diameter, with one or two punctiform nucleoli. 



The multiplication of the species is effected principally by cysts. 

 Encystment takes place only between individuals with a single nucleus 

 and of spherical form. The two conjugated organisms secrete around 

 them successively several envelopes, each marked with an equatorial 

 line of dehiscence. 



The phenomena which succeed one another in the cyst are very 

 peculiar. Each of the two nuclei divides so as to produce three nuclei 

 in the corresponding half of the cyst. Of the six nuclei thus produced, 

 only two take part in the constitution of the reproductive elements, 

 represented exceptionally by two small spores, and normally by a 



* Comptea Rcudus, xcvi. (1883) p. 1378. 



