REPORT ON THE RADIOLARIA. Ixv 



they melt into short, thick, hyaliue rods, the so-called " gelatinous cilia." The myo- 

 phiiscs are found only in the order Acanthometra, and are wanting in the 

 Acanthophracta, as well as in the other three legions of Eadiolaria. 



A. The " ciliary coronas " on the skeletal rods of dead Acaut hornet ra were first 

 described by the discoverer of this order, Johannes Miiller, and referred to as " the stumps of the 

 contracted, thickened threads " (L. K 12, p. 11, Taf. xi.). 



B. The " nuvihcr of the gelatinous cilia" I found constant in certain species of Acantho- 

 metra, and stated in my Monograph (L. K 16, p. 115) "that here is to be found the first 

 differentiation of the diffuse sarcode into definite organs of regular definite number, size, and 

 position, which deserve the name tentacles rather than pseudopodia." 



C. The nature of the myophriscs as fibrillin? allied to muscles was first discovered by E. Hertwig, 

 who described them as " structures of peculiar nature," under the name of " contractile threads," and 

 pointed out in detail their histological and physiological peculiarities (L. N. 33, pp. 16-19, Taf. i.). 



97. The Exoplasm of the Periijylea. — The extracapsular protoplasm of the 

 Spumellaeia or Peripylea is in communication with the intracapsular sarcode by the 

 innumerable fine pores of the capsule-membrane, and like these pores is evenly 

 distributed over the whole surface. The sarcomatrix which immediately surrounds the 

 central capsule is moderately strong, and sends out innumerable long, thin pseudo- 

 podia, which probably correspond to the pores of the membrane. Their number is 

 markedly greater in the Spumellaeia than in the other three legions. The ramifica- 

 tions and communications which the radiating fibres of the sarcomatrix undergo 

 within the calymma, apparently present the most manifold variations, so that the 

 sarcoplegma or intracalymmar network thus formed has very diverse forms. On the 

 surface of the calymma the exoplasmic threads constitute a variously disposed sarco- 

 dictyum, a regular or irregular exoplasmic network, by the silicification of which a 

 primary lattice-shell arises in the majority of the Spumellaeia. The free ends of the 

 pseudopodia, which arise from this extracalymmar network and radiate out into the 

 water, appear in most Spumellaeia to be relatively short, but exceedingly numerous. 

 Specially modified pseudopodia and axial threads in particular do not seem to occur in 

 this legion. Perhaps, however, among the latter may be reckoned the remarkable 

 pseudopodia which combine to form the sarcode flagellum in many Discoid e a (and 

 perhaps in other Spumellaeia). This axoflagellum is a particularly strong thread of 

 sarcode, arising from a definite point in the central capsule ; it is cylindrical or 

 slenderly conical in form, much longer, stronger, and more contractile than the ordinary 

 pseudopodia ; it contracts in a serpentine fashion on mechanical irritation and seems to 

 originate by the fusion of a bundle of pseudopodia (compare § 95, C). 



98. The Exoplasm of the Actipylea. — The extracapsular protoplasm of the 

 Acanthaeia or Actipylea differs in several important respects from that of other 



(ZOOL. CHALL. EXP. — PART XL. 1886.) Rl i 



