672 SUMMARY OF CURRENT RESEARCHES RELATING TO 



wliicli obtains in existing forms. All the species of Miliolites that 

 they have studied have, therefore, been found to be dimorj)hou8. 

 Two hypotheses present themselves, when an ex]>lanation is sought 

 for We may either suppose that each species is represented by two 

 forms distinct from their origin, though this is opposed by the fact 

 that very young individuals of the second form (" form B ") have never 

 yet been detected ; or, the dimorphism may be regarded as " the result 

 of a final evolution " ; in such cases every individual would pass 

 through two successive phases ; and it is important to note that in all 

 the species examined, exact measurements showed that, were the 

 central chamber to be absorbed, the space thus set free between the 

 first serial chambers in " form A " would be large enough to allow the 

 modified chambers of " form B " to be developed. To judge between 

 the value of these two hypotheses the authors propose to trace a 

 living form through all its develojDmental phases. 



New Type of Arenaceous Rhizopoda.* — H. B. Brady describes a 

 new genus of Arenaceous Rhizopods to which he applies the name of 

 Syringammina ; the test is extremely fragile, owing to the fact that its 

 walls are composed of fine sand with scarcely a trace of inorganic 

 cement, while, owing to its considerable size — the figured specimen is 

 about an inch and a half in diameter — it can scarcely support its own 

 weight, when taken out of water. Examination of a fractured surface 

 reveals a congeries of branching and inosculating tubes, radiating 

 from a common centre. Near the perii)hery the system of tubes takes 

 a distinctly radial character ; these tubes are not of uniform diameter, 

 being no more than • 5 mm. near the centre, while they may be twice 

 as wide near the exterior. 



So far as its nearest living allies are concerned, this new genus 

 stands closest to Asirorhiza, but it is distinguished by the great number 

 of its tubes ; from Parkeria it is to be distinguished by the fact that 

 there is no cancellation of the layers, and among fossil Rhizopods it 

 will probably be found to be most closely allied to those which Prof. 

 Duncan has grouped together as Syringosphseridse. 



Fully formed Embryos within a Rhizopod. f — Some embryos 

 of Peneroplis p-oteus D'Orbigny, were found by C. Schacko within the 

 chambers of an adult, itself extracted from the intestine of a 

 Holothurian. In the last large chamber were found 30 embryos 

 in two rows, and each of the same size as the embryonal chamber of 

 the mother, and in the next chamber 26 ; in the whole of the succeed- 

 ing narrow chambers, 60 more embryos occurred, some of them of 

 irregular form. These embryos appear to have originated by regular 

 segmentation of the sarcode or by breaking up of the whole soft 

 parts into equal portions, as occurs in the central capsule of Radiolaria 

 during reproduction. The young are probably released by the bursting 

 of the maternal chambers owing to pressure from within, exercised 

 by the young. The presence of irregularly formed embryos may 



* Proc. Roy. Soc, xxxv. (1883) pp. 155-61 (2 pis.). 



t SB. Gfsell. Naturforsch. Freunde Berlin, 1882, pp. 130-2. 



