82 THE FORAMINIFERA 



was described by M. Schultze (64, p. 55), the shape is oval, and 

 there is a single orifice (Fig. 15), but Schaudinn finds (43) that 

 when living amongst the stems of algae, it loses its oval shape 

 and assumes a branching form, new mouths being developed at 

 the ends of the branches. Such branched forms may attain a 

 length of 5 mm. 



Two modes of reproduction were observed. One is by a 

 process of fission, the body slowly dividing into two or three 

 parts, sometimes of unequal sizes ; the other is by the formation 

 of zoospores. In the latter process the pseudopodia are retracted 

 and the whole protoplasm divides up into oval or pear-shaped 

 bodies, 5-8 p. in diameter, containing a nucleus 3-6 p. in diameter, 

 a vacuole, and a conspicuous granule. They swim by means of 

 a single flagellum 30-38 //, in length. 



The zoospores conjugate in pairs, but in this case the conju- 

 gation is, according to Schaudinn, between members of the same 

 brood. The further history of the zygote could not be followed. 



The formation of the zoospores of Hyalopus is evidently com- 

 parable on the one hand with the reproduction of Trichosphaerium 

 which gives rise to the "amphiont" generation, and on the other 

 hand with the reproduction of the megalospheric form of Polysto- 

 mella. 



A similar mode of reproduction to the slow process of fission 

 of Hyalopus has been seen in Lieberkiihnia and Lecythium, the 

 division of the protoplasm involving that of the envelope. Whether 

 this is to be compared with the production of the brood of 

 melagospheres by the multiple fission of the microspheric parent, 

 or to the similar slow fission which occurs in Trichosphaerium in 

 addition to the multiple fission of the "amphiont" parent, it 

 appears to be at present impossible to decide. Many of the 

 Gromiidea have a single orifice to the test, as in Gromia and 

 Euglypha (Figs. 1 and 3). Shepheardella and Amphitrema have two 

 orifices, situated at either end of a median axis (Fig. 16, 5 and ll). 



ORDER Astrorhizidea. 



In Saccammina, and some other members of the Astrorhizidea 

 in which growth is accompanied (as explained above, p. 54) by 

 expansion of the test, no evidence on the phase of life-history 

 represented, is furnished by its structure. But in other genera, 

 such, for example, as Hyperammina, in which the tests grow not 

 by expansion, but by addition, a large globular chamber is some- 

 times found at the commencement (Figs. 17, d, and 18). Such 

 forms may well represent a megalospheric generation. There 

 is, however, no evidence at present of the microspheric forms 

 corresponding to them. 



Rhumbler has made a careful investigation (33) of the nuclear 



