292 PKOr. ALL5JJl>' 0>" the HECE^fl eeseabches 



admit the presence of hard skeletal structures. The evidence, 

 however, appears to me to be against the view thas taken by the 

 German mieroscopists. 



Among the forms described by Archer as developing no hard 

 parts in the outer zone is the genus Set erophri/s, Archer (fig. 12). 

 In this there is a central spherical body-mass differentiated intoen- 

 dosarc and ectosarc, having in the endosarc a single nucleus, and in 

 the ectosarc contractile vacuoles. The investing zone is traversed 

 by long, granular, unbranched and non-anastomosing pseudopodia, 

 and its periphery is extended into radiating processes of various 

 lenoih and fineness in the different species. These processes are re- 

 trarded by Archer as simple extensions of the surface of the invest- 

 ing laver. which he believes to be entirely destitute of hard parts, 

 while Hertwig and Lesser regard them as spines, and accordingly 

 place the genus SeteropTirys among their SeJiozoa slceletophora. 



Between such able observers it is difficult to decide : but it 

 appears to me that the weight of evidence is in favour of Archer's 

 iuterpretation, and that SeteropTiri/s has no hard parts which can 

 be recrarded as constituting a skeleton Hke that in the true ske- 

 letophorous Heliozoa. 



The enveloping zone has the itppearance of being separated 

 from the proper body by a narrow clear interval. This, as main- 

 tained bv Archer, is probably only an inner layer of the zone more 

 homo£:eneous and pellucid than the rest. 



In S. myriopoda, Archer, the ectosarc of the spherical body- 

 mass contains a dense layer of chlorophyl granules which lies just 

 beneath its surface. 



Among Heliozoa with well-developed skeleton must be uieu- 

 tioued the species of AcautTioei/stis. Tlie genus AeanfJiotysfis had 

 been founded by Carter on the ActinopTirys tiridis of Ehrenberg ; 

 and what he regardsas a second species of this genus has been de- 

 scribed bv him under the name of AcanfTioei/sfi's turfacea (fig. 13). 

 This is a beautiful little green rhizopod, which occurs in moor- 

 pools ; and Greeff now gives us the results of some fixrther eareftil 

 observations he had made on it*. 



Prom the sitrface of its spherical body, which is filled with green 

 cn*anules, and contains a great number of vacuoles and certain 



* " Ueber Eadiolarien <S:c. des sussen "Wagsers," Arehiv f . mikr. Anat. t. 

 1869. Both Greeff and Grenacher regard A. turfacea. Carter, as identical with 

 the Actinophrys ririJis of Ehrenberg : but the corre<*nes of this determination 

 is not admitted bv Archer or bv Hertwig and Lesser. 



