Dr. G. C. Wallich on the Thalassicollidae. 101 



the digestive cavities of Hydrozoa of far too minute size to 

 have been able to swallow them in the aggregated state*. 



The most remarkable feature in Thalassicolla nucleata 

 (Huxley) consists in the presence of the " delicate flattened 

 branching fibrils/' which are described as being " beset with 

 exceedingly minute dark granules like elementary molecules, 

 which are in active motion as if circulating along the fibrils, 

 but without any definite direction " — and likewise in the occur- 

 rence of the " yellow cells " (sarcoblasts) amongst the deeper- 

 seated vacuoles j". If we regard the "fibrils" here alluded 

 to as pseudopodial filaments (and it is difficult to regard them 

 in any other light, if the organism belongs at all to the Rhizo- 

 podal group), it is manifest that the cyclosis cannot be depen- 

 dent on a contractile power resident in those portions of the 

 structure of the typical forms that exhibit a similar phenome- 

 non, but must be the result of a contractile power inherent in 

 the gelatinous matrix by which the " fibrils " are surrounded, 

 as stated by M. de Quatrefages to be the case in Noctiluca 

 miliar is%. On the other hand, according to Huxley, it would 

 seem highly probable that the cyclosis, together with the di- 

 vision and inosculation of the fibrils in Noctiluca, are " abnor- 

 mal states, and that in the natural and perfectly unaltered 

 condition the fibres and fibrils are perfectly quiescent, and 

 present nothing to be compared to the Protean movements of 

 the Amaba}"§, the conclusion he arrives at being that 

 Noctiluca tl is no Rhizopod, but must be promoted from the 

 lowest ranks of the Protozoa to the highest." If the latter 

 view be correct, the true position of Thalassicolla nucleata must 

 still remain somewhat doubtful ; for it is obvious that the 

 granular circulation and the presence of the fibrils are in 

 reality the principal characters upon which the Rhizopodal 

 character of that organism can be assumed. 



Although I have had ample opportunity of examining 

 Thalassicolla nucleata in the tropical and subtropical seas on 

 both sides of Africa, I have never been able to satisfy myself 



* Specimens of composite Thalassicollidae when preserved in spirits 

 usually break up, and accordingly yield no reliable evidence, one way or 

 the other, as regards the question under discussion. In spirit-specimens, 

 and also in such as have been preserved on slides, I have now and then 

 detected what appeared to be the spherical-shelled and the spicular forms 

 within the same gelatinous envelope; but I regard the chances of mis- 

 interpretation as too great in such a case to admit of my stating that 

 their juxtaposition is normal, however probable this maybe. 



t Huxley on Thalassicolla, he. cit. p. 435. 



\ See observations by this distinguished French naturalist in Huxley's 

 paper on Noctiluca, ' Quarterly Journal of Microscopical Science/ vol. iii. 

 p. 61. 



§ Luc. at. p. 51. 



