THE FORAMINIFERA 123 



Max Schultze was the first to demonstrate the spiral arrangement 

 of the early chambers, and its dimorphic character was shown, as 

 we have seen, by Merkel. 



The life -histories of Patellina corrugata, Will, and Discorbina 

 globularis, d'Orb., as exhibited by specimens living in aquaria, have 

 been investigated by Schaudinn (45). Ordinarily the protoplasm 

 contains many granules which, during life, obscure the nuclei, but 

 by excluding animal food, and limiting the diet to the diatoms 

 growing on the sides of the vessels, Schaudinn succeeded in ren- 

 dering the nuclei visible, so that their changes could be followed 

 in the living animal. 



The form of reproduction observed was that comparable 

 with the production of broods of megalospheric young by a 

 megalospheric parent, and Schaudinn's account of the changes 

 which the nuclei undergo is the fullest which we yet have of their 

 behaviour in this phase of the life-history of the Foraminifera. 



All the specimens which came under notice contained a single 

 nucleus in their early stages. As the reproductive phase approached 

 the nucleus became segregated into a number of parts (usually 

 7-10), which were dispersed in the protoplasm, and in some cases 

 became subdivided by a similar process, so that there may be as 

 many as 30 nuclei of unequal sizes. The protoplasm becomes 

 divided up about the nuclei into masses proportional to them in 

 size, and the young thus produced repeat in turn the same cycle 

 of development. In Discorbina the division to form the young 

 occurs within the parent test, from which they escape by the 

 resorption of its walls. In Patellina it occurs in the large umbilical 

 space, e.g. outside the parent test. Schaudinn is inclined to the con- 

 clusion that in these species the stage in which zoospores are pro- 

 duced has been lost from the life-history, and that reproduction 

 takes place only in the manner described. Thus he regards these 

 species as having been originally dimorphic, but now monomorphic. 



I have measured the central chambers of a number of stained 

 and mounted specimens of Discorbina globularis collected from the 

 seashore, and the results are shown in Fig. 52. It will be noticed 

 that in this species the central chamber is on the whole remarkably 

 small. In the great majority it varies in size from 12 to 31 />t, the 

 average of 159 specimens being 19 /x. In one case it was only 

 9 ^ in diameter. 



In this species the chitinous element of the shell is very 

 abundant, and forms an obstacle to the penetration of staining 

 reagents, but 54 of these specimens afford an indication of the 

 nuclear condition. In 48, including two with a central chamber 

 16 /x in diameter, a single nucleus is present, and in one of the 

 remainder a large nucleus is killed in the process of breaking up 



