BULLETIN 71, UNITED STATES NATIONAL MUSEUM. 



Chapman has demonstrated the two forms of Alveolina, and the 

 series of these larger forms is now nearly complete. 



To Lister and Schaudinn we owe much of the knowledge of the life 

 history of the Foraminifera and the relation of dimorphism to the 

 life cycle. Many other investigators have added, in greater or lesser 

 degree, to our knowledge of the Foraminifera, but the names noted 

 above stand out prominently in the history of the work in the devel- 

 opment of the Miliolidae. 



Proloculum. — The proloculum or initial chamber of the Forami- 

 nifera as seen in the Miliolidae consists of an oval or subspherical 

 chamber. The test of the proloculum in some genera (Peneroplis, 

 Orbiculina, and Orbitolites) is clearly perforate, while this character 

 has not been made out in other genera. 



The proloculum is the first distinct stage in the development of the 

 test. Although in the Miliolidae there is no distinctly single cham- 

 bered form which may be con- 

 sidered as the radicle (like 

 Lagena for the family of the 

 Lagenidae) , it is fair to assume 

 that there was in the early de- 

 velopment of the group a sin- 

 gle - chambered form. This 

 radicle, although not defi- 

 nitely known as an adult, is 

 represented by the proloculum 

 or first stage in the develop- 

 ment of the many chambered 

 forms of the family. The size 

 of the proloculum is of great 

 importance, as will be consid- 

 ered in later discussion. 

 Characters of the "embry- 

 onic" young of Miliolidae. — The production of young in a number of 

 genera of the Miliolidae has been noted by several observers. The 

 young individuals are formed inside the chambers of the adult test, 

 especially in the outer and larger chambers. The characters through- 

 out the family in this "embryonic" stage seem to be very uniform. 

 A detailed description of this stage in the development will be useful 

 for later comparison. 



The young individual (fig. 1) when set free from the "mother" cell 

 consists of two distinct stages in its test characters. The first cham- 

 ber is a globose proloculum in all normal individuals. Exceptions to 

 this condition will be noted later. The second chamber consists of a 

 nonseptate tube close coiled about the proloculum. Seen from the 



Fig. 1.— "Embryonic young" of miliolidae, in this 

 case of Peneroplis, taken from the "mother test." 

 (After Schacko X 420.) o, Longitudinal section 



SHOWING THE PROLOCULUM, OVAL IN SHAPE FOLLOWED 

 BY THE LONG CORNUSPIRA-LIKE SECOND CHAMBER; THE 

 WALL OF THE TWO CONTINUOUS AND OF THE SAME THICK- 

 NESS. 6, TRANSVERSE SECTION SHOWING THE SECOND 

 CHAMBER AT THE TWO SIDES OF THE PROLOCULUM, THE 

 UNIFORM SINGLE WALL AND THE FLATTENING OF THE 

 SIDES OF THE PROLOCULUM WHERE THE SECOND CHAM- 

 BER IMriNGES UPON IT, AN ADDED PROOF THAT THE TWO 

 ARE FORMED AT THE SAME TIME. 



