SEX IN PRCriOZOA 183 



spring-, \\hilc the anisosporcs ;irc thought to he gametes. However, 

 there is nuich confusion in the Hterature on the subject. 



Although the Radiolaria had been the objects of study from the 

 rirst half of the nineteenth century onward, Cienkowski (1871b) 

 and I Icrtwig (1876) were among the first to report the two kinds of 

 swarmers and Haeckcl (1887), in his Challenger Report, indicated 

 his belief that sponilation was the common method of reproduction 

 in Radiolaria. 



Brandt (1885) studied the Sphaerozoon group (colonial, Peri- 

 p\Iea) at Naples and recognized, besides the s\^'armers, young vege- 

 tative, young reproductive, old vegetative, and old reproductive 

 stages. The last stage produced the isospores and anisospores. Some- 

 what diverse conditions were found even within the same genus. For 

 example, for CoUozowii he found both isospores (Fig. Q, 2, 3) and 

 anisospores in C inervie (4, 5) and C. piilvuluvi, but only isospores 

 in C. pelctgicuvi and only anisospores in C. hertwigi. Similar differ- 

 ences occurred in the genus Sphaerozowii (6 to 9). Different condi- 

 tions prevailed in different groups. For example, in the Collosphae- 

 rida microspores and macrospores developed in different individuals, 

 the "spores" being spindle-shaped and sometimes having a crystal, 

 while in the Sphaeroida macro- and microspores developed in a single 

 individual (1), the "spores" being bean-shaped and wdth or without 

 a crystal; isospores generally were spindle-shaped and had crystals. In 

 all cases except the acanthometrids (which belong to the Actipylea) 

 the "spores" had two flagella. Like his predecessors, Brandt was un- 

 able to follow the development of swarmers to the young vegetative 

 stages. 



Enriques (1919) also studied the colonial Radiolaria, finding 

 "zoospores" in three species of Collozoimt, two species of Sphaero- 

 zoiim, and one species of CoUosphaera. He also reported macro- and 

 microspores (anisospores) in two species CoUozoimi and one species 

 of Spbaerozoiim, but saw no fusions among the ffagellispores. 



In 1905 Brandt found in ThalassicoUa jjucleata (Peripylea) that 

 some individuals developed only isospores and others only anisospores. 

 The isospores (Fig. Q, 14 to 17) in life w^re rather wedge-shaped or 

 spindle-shaped, but always with two flagella, not one, as stated by 

 Hertwig. The anisospores differed considerably in size, the macro- 

 spores being 16 to 17 [i- long and the microspores only 8 to 10 [j. long. 

 Both kinds had rounded ends and slanting furrow^s near the middle. 



