44 SYNOPTIC COLLECTION. 



mal nature, gives forth carbon dioxide. This supplemen- 

 tary relation where there is a mutual dependence of the 

 one upon the other, is known as symbiosis and will be 

 found to- occur among other more specialized animals. 



The division of the nucleus takes place early in life and 

 this is a fact of great significance. The law of accelera- 

 tion in development which has been demonstrated in many 

 groups of the Metazoa, may have acted in this case, caus- 

 ing the characteristic late nuclear division peculiar to 

 the single Radiolaria, like Actissa, to appear early in the 

 life of the zoon. After the division the process of spe- 

 cialization is carried on in a most interesting manner, as 

 shown in figs. 6-9, and results finally in the formation of 

 the asexual isospores and the probably sexual aniso- 

 spores. Fig. 6 is a zoon in the act of forming isospores. 

 The original central nucleus has divided into many nuclei, 

 and its place has been taken by a large oil globule. The 

 nuclei lie close together but do not press upon each other 

 sufficiently to be flattened into polyhedrons. The crystals 

 first appear like lengthened granules and one is laid close 

 to a nucleus. Gradually they grow into the form shown 

 in fig. 6. In fig. 7, a, b (a diagrammatic representation of 

 later stages in the process), the nuclei and crystals have 

 arranged themselves near the periphery, while the large 

 oil globule remains in the center. Finally disintegration 

 takes place and the isospores appear. Fig. 8 is a dia- 

 grammatic representation of the process of forming aniso- 

 spores drawn from balsam preparations. In early stages 

 (fig. 8a, fig. 9) irregular groups of differentiated nuclei 

 occur in spherical masses of plasma (fig. 9 shows a group' 

 of three nuclei in such a spherical mass) , and in the inter- 

 substance between these are found large, homogeneous 

 nuclei, sometimes drawn out to a point at either end (fig. 

 9b). With the diminution of the central oil globule there 

 appear the grape-like clusters of fat seen in figs. 8 a, b, 

 c. In fig. 8b (a later stage than 8a) the groups of 

 nuclei have increased in number and the homogeneous 



