84 TOILERS IN THE SEA. 



in the testaceous (or shell-bearing) forms, that the 

 deposition of the shell material dates, as a general 

 rule, from this period ; the development of the ' testa/ 

 while still within the parent sarcode, occurs in some 

 of the Foraminifera, and brings the phenomenon 

 within the category of viviparous reproduction." 1 

 These sarcoblasts are very conspicuous in the Poly- 

 cystins, and are more readily seen than in the Fora- 

 minifera, in consequence of the crystalline character of 

 the skeleton. They occupy a position for the most 

 part immediately within the silicious framework. 



No better illustration of Dr. Wallich's views on 

 this, which was then considered an important phase 

 of the life history of the Polycystins, can be given 

 than in his own words: "In 1863," he writes, " I 

 pointed out, for the first time, that the so-called 

 * yellow bodies,' as also more or less perfectly colour- 

 less, but in other respects perfect homologues of them, 

 are present throughout all the Rhizopodal families, 

 both oceanic and fresh-water ; this statement being 

 based on long personal experience. At the time indi- 

 cated, they had been observed by others only in three 

 pelagic families, their brilliant yellow tint in the 

 pelagic families being regarded as their distinguishing 



1 Dr. Wallich : Quart. Journ. Micr. Science (1865), p. 71. 

 Afterwards Cienkowski in 1871, and Brandt in 1881, have 

 shown that the "yellow cells" do not belong to the Radiolarian 

 system, but are symbiotic unicellular Algae. 



