1897.] of Triloculina and Biloculina. 239 



the conjugation of zoospores in Hyalopus*, a form however in 

 which dimorphism has not been shown to exist, yields it consider- 

 able support. 



If we apply this probable, though still insecure result to the 

 problem presented by the Miliolidse, we find that while the 

 asexually-produced megalospheric form has a direct development, 

 the sexually-produced microspheric form goes out of its way to 

 repeat the arrangement characteristic of allied forms before it 

 attains the arrangement proper to its own genus. 



Is not this a particular instance of a phenomenon widely met 

 with in higher forms of animals, in which the individuals produced 

 by budding attain the adult structure by a direct development, 

 while those produced from the egg often develope by an indirect 

 course, going out of their way to repeat lost features characteristic 

 of the archaic forms of their race ? To give an instance, the 

 ascidians belonging to the genus Clavellina develope asexually by 

 buds which grow out from the stolons at the base of a colony and 

 are fashioned directly into the adult form, while the result of the 

 development of the fertilised egg of Clavellina is to produce a 

 tailed larva wholly unlike the parent and recalling the free 

 swimming Appendicularice. 



In the case of higher animals the larval stages are lost, the 

 body of the larva being fashioned into that of the adult, but in 

 this group of the Protozoa, the Miliolidce, the peculiar structure of 

 the young is permanently recorded, being built in and retained in 

 the centre of the chambers subsequently added. 



While many of the biloculine and triloculine forms of the 

 Miliolida? present the contrast in the mode of growth of their 

 megalospheric and microspheric forms, above described, in a very 

 marked manner, I feel that the case in favour of the explanation 

 here offered is to some extent weakened by the existence of excep- 

 tions presented by certain species belonging to the trematophorine 

 Miliolidae, and especially by Idalina antiqua (d'Orb. sp.), whose 

 structure has been elucidated by M. M. Munier-Chalmas and 

 Schlumberger-f-. 



In this species, whose growth in its later stages is mainly on 

 the biloculine type, the first formed chambers of the megalospheric 

 form are in some cases, though not in all, disposed as in the 

 microspheric form, on the quinqueloculine plan. Here then both 

 megalospheric and microspheric forms of the species may, in the 

 early stages of growth go out of their way to repeat the mode of 

 growth characteristic of the genus Quinqueloculina. The authors 

 point out that the megalospheric form does in some cases grow on 



* Sitz. Ber. Geselhch. Naturforsch. Freunde Berlin, Jahrp;. 1894. 

 t Note sur les Miliolidees trematophorees. Bull, de la Soc. Geologique de 

 France. 3 e Ser. t. xm. (1885), p. 273. 



