8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. '/J 



to the law of recapitulation, in which an animal repeats in its own 

 development certain of the stages in its ancestry. Thus the test of 

 Biloculina, at least in the niicrospheric form, shows stages com- 

 parable to the fully developed characters of Cornuspira, Quinquelocu- 

 lina, and Trilocul'ma, before the adult character of Biloculina is taken 

 on. In the megalospheric form, certain of these earlier stages are 

 often skipped. 



These early stages are important from the point of view of classi- 

 fication. Nearly all the Textulariidae have in the microspheric form 

 a coiled early development closely allied to certain of the Lituolidae, 

 and show that the alternate (Textularian) character was derived 

 through a coiled ancestry. 



Likewise in Peneroplis and others of the Miliolidae the very earliest 

 stages show a perforate test, and make clear that the imperforate 

 character is an added one and that the Miliolidae are therefore a 

 fairly new group derived from a perforate ancestry. Instead of being 

 a primitive group as earlier thought, the Miliolidae are high in the 

 scale, a fact made further evident by their geologic history. 



From the study of developmental stages, coupled with fossil evi- 

 dence, will come a more sound classification of the group than obtains 

 at present. 



VARIATION 



From statements made by many of the earlier writers on the 

 foraminifera, it would seem that there is a very great variation in 

 the group. From my own observations this does not seem to hold. 

 In the case of Ammodiscus incertus, several hundred specimens were 

 measured, and the amount of variation in respect to size of chamber, 

 size of test and thickness, when reduced to ratio of the size of the 

 initial chamber, was practically negligible. If stages of development 

 are taken into consideration, and the differences due to the micro- 

 spheric and megalospheric forms are considered, the actual variation 

 left in adults is less than in most other groups of animals. When 

 specific lines are drawn more sharply than at present, as will be done 

 as more material is studied, the variation will be more apparent than 

 real. 



DISTRIBUTION IN PRESENT OCEANS 



So far as dredging operations have been carried on, the foraminifera 

 seem to be distributed over every part of the ocean bottom. Expe- 

 ditions into both polar regions have shown that the ocean muds 

 of the polar seas have an abundant foramini feral fauna. In the 

 shallow water of all the oceans they are abundant. In the deep 



