788 SUMMARY OF CURRENT RESEARCHES RELATING TO 



interested in its subject, and not the less so that our knowledge 

 regarding these organisms is at the present time in so scattered and 

 undigested a condition. 



Protochytrium Spirogyrse, a new Myxomycete (?).* — A. Borzi 

 describes a parasitic organism of very low organization, which he 

 finds in the cells of Spirogyra crassa and of a few other nearly allied 

 species of algae, rapidly destroying the contents of the cells and 

 causing complete disintegration of the filaments, the cell-walls them- 

 selves ultimately entirely perishing. The minute masses of proto- 

 plasm of which it is composed are completely destitute of cell-wall, 

 and display amoeboid motions, but without any pseudopodia. They 

 derive their nutriment directly from the surrounding protoplasm, and 

 may be regarded as plasmodia of very reduced dimensions. They 

 are composed of homogeneous protoplasm, within which are very fine 

 granulations, and have, therefore, all the characters of an organiza- 

 tion the simplest that can be imagined. They compose a true jalo- 

 plasm in the sense of modern histologists, constantly altering its 

 form in consequence of its amoeboid motions. The granulations are 

 frequently disposed round a small transparent central areole, which 

 represents a true vacuole. It is, however, entirely destitute of true 

 nuclei, the minute granulations wanting all the characteristic struc- 

 ture of these organisms. The central vacuole is constantly altering 

 its position, and alternately contracting and expanding. The princi- 

 pal, if not the sole, agent in these amoeboid movements appears to 

 be the superficial protoplasmic layer. The growth of these organisms 

 is rapid, and they attain a diameter of about 40 fj. in twelve hours. 



The process of nutrition may be divided over two distinct 

 periods. In the first the nutriment, derived from the surrounding 

 substratum, passes directly into the body of the parasite. In the 

 second period, the substances, already ingested and deposited, become 

 somewhat elaborated and digested. These two phases can be well 

 followed under the Microscope. 



When one of the plasmodia comes into contact with a band of 

 chlorophyll, it slowly penetrates into its interior. A small portion 

 of the nutrient substance, consisting of protoplasm containing chloro- 

 phyll and of starch- grains, becomes at length entirely imprisoned in 

 the mass of the plasmodium. The ingested substance retains for a 

 very short time its original properties. The chlorophyll soon loses 

 its green colour ; the granules of starch are the last portion to be 

 completely absorbed. An excretory portion which is not digested 

 is finally expelled. 



The vegetative activity of the plasmodia ceases on the commence- 

 ment of the reproductive period ; they attain a state of quiescence, 

 and the formation of zoosporangia commenecs. The peripheral 

 layer of protoplasm becomes thinner and tends to merge in the 

 internal portion; its motility at the same time disappearing alto- 

 gether. After numerous internal changes in the structure of the 

 protoplasm, the contents divide by successive bipartitions, either a 



* Nuov. Giorn. Bot. Ital., xvi. (1884) pp. 5-32 (1 pi.). 



