PROTOZOA. 37 



but the internal structure of many species of this genus 

 shows it to be more specialized than Globigerina. In 

 slide No. 36 a number of Orbulina shells are seen with 

 Globigerina-like shells inside. (The broken yellow speci- 

 men on the slide is probably another genus.) PI. 37, fig. 

 i, is Orbulina universa d'Orbigny, in which the Globige- 

 rina-like shell in the interior is not wholly covered by the 

 exterior spherical shell. Fig. 2, a surface specimen, 

 shows the covering entire but thin, so that the inner shell 

 can *be easily seen through it. Fig. 3 is the Globigerina- 

 like shell from which the outer Orbuline sphere has been 

 removed. The shell is provided with spines, like most 

 surface specimens, and its chambers are partly or wholly 

 filled with .protoplasm. In fig. 4, a bottom specimen, the 

 inner shell is not seen, owing to the thickness of the wall. 

 Fig. 5 is an old bottom specimen in which the inner shell 

 does not exist but the wall is laminated, giving the 

 appearance when seen under the microscope of spheres 

 within spheres. This laminated appearance is observable 

 in some of the specimens in the microscppic preparation 

 No. 36. According to the observations of Shacko, 1 which 

 were made on bottom specimens, only the young Orbu- 

 linae have Globigerina-like shells, while in very large and 

 old bottom specimens they do not occur. 



From the observations made on Globigerina and Orbu- 

 lina it may be possible that we have here only one genus. 

 In such a case, the youngest or nepionic stage would be 

 represented by a single thin-walled hollow sphere ; the 

 adolescent or neanic stage by several spheres fastened 

 together ; the mature or ephebic stage by several united 

 spheres completely enclosed in the last globular chamber ; 

 and the old age or gerontic stage by a single hollow 

 sphere, the thick wall of which is laminated. Either this 

 is the case or else Globigerina is the more primitive, 

 ancestral form, which in course of time was developed 



!Arch. f. Naturgeschichte, XLIX, I, 1883. 



