148 W. H. HARRIS ON MARINE MICROSCOPIC VEGETABLE ORGANISMS, 



avoidance of each other's paths may be that they extract from 

 their mineral habitat, beyond the limits of the plant, an element 

 necessary to then- development. I have previously shown, on the 

 evidence of a decalcified mineraHsed specimen, that they are 

 capable of fracturing the containing material beyond the actual 

 limits of their growth, and that would favour this view. 



The avoidance of each other deprives us of the idea of anything 

 approaching conjugation in such species. But this characteristic 

 is not universal throughout the group, for such species as grow in 

 small tufts erode the shells into comparatively deep pits by the 

 branches coalescing towards the central point ; and in another 

 instance — viz., 4. reticulata — the most prominent feature is the 

 beautiful net-Hke appearance of the plant caused by the coales- 

 cence of the branches which it so freely produces. 



Selective Powei's. 



There are indications, I am disposed to think, that the 

 organisms display a partiality for certain material in the selection 

 of their habitat ; nor need this be matter for surprise, as all 

 animated nature exhibits the same phenomenon. It would, 

 indeed, be a strange departure from a natural law if they 

 deviated from the rule which governs the better-known classes 

 of the animal and vegetable kingdoms. 



I have stated that these plants invade Foraminifera ; when, 

 however, a critical examination is made it becomes evident that 

 they do not indiscriminately attack the enth-e order, but that 

 they exhibit a decided preference for the members of the hyaline 

 group ; their invasion of the porcellaneous division is exceedingly 

 rare. I have occasionally met with a few very minute specimens 

 of Lacunae in different species of the sub-family Miliolinse, and 

 a small, undetermined, branching species in the tests of 

 Orbitolites. Beyond these I have no record. 



The hyaline species are attacked in different degrees. Thus, 

 the tests of Operculina complanata are frequently crowded 

 with various species ; Amphistegina lessonii and CychclypeuB 

 guembelianus more sparingly, still less so the tests of Textularia, 

 and some of the sub- families of the Lagenidae and Rotalinie. 

 My record for the Globigerinidae consists of a few filaments of 

 an undetermined species. 



Entomostracan valves are plentiful in some dredgings, but for 



