NOTES AND MEMORANDA. 73 



more irregular and angular. The protoplasm meantime advanced 

 from within towards the cuticle, which sank in somewhat and became 

 folded. The original spherical form of the animal became very 

 sensibly flattened. Attempts to produce a fresh generation of gas 

 unfortunately could not be made. 



The second case relates to a form allied to, if not identical with 

 Amoeba radiosa. It was obtained by a pipette from the surface of some 

 water pretty thickly covered with Lemna. Amongst several specimens 

 one was found which measured about • 15 mm., and was furnished with 

 about twenty short, irregular, and pretty broad conical protuberances, 

 which in the interior contained a perfectly spherical air-bubble about 

 • 05 mm. in diameter. This continually diminished from the moment 

 the animal came to be examined. Within three minutes it had dis- 

 appeared, and he did not succeed in observing a new generation of 

 air. 



Since, therefore, the presence of gas-bubbles in living protoplasm 

 has been confirmed in three forms of Protozoa lying widely apart 

 from each other, it may be considered probable that the phenomenon 

 is still further extended ; but as he is only seldom in a position to pay 

 attention to the subject, Professor Engelmann asks those of his fellow 

 explorers in the same field, who have more frequent ojiportunities, to 

 investigate the matter. Success would doubtless be best attained if 

 the animals are taken from the surface of the water and examined as 

 quickly as possible. 



On this communication Professor Geza Entz, of Hungary, 

 writes:* — " Eeferring to the account given by Professor Engelmann 

 of the interesting phenomenon of gas-bubbles in the protoplasm of 

 Protozoa swimming on the surface of water, I have had an oppor- 

 tunity of observing it, not only in Arcella and Amoeba, in which (espe- 

 cially the former) it occurs with great frequency, but several times in 

 Difflugia proteiformis also. The latter had always only one, but that 

 a very large gas-bubble, occupying almost half the body ; it gradually 

 diminished whilst under examination, finally disappearing without 

 leaving any trace: the Arcella Skudi Amoeba, on the other hand, often had 

 several bubbles. Once I observed in an Arcella a bubble between the 

 shell and the body of the rhizopod, which forced itself to the mouth of 

 the shell and finally out from beneath it, like an air-bubble out of 

 a submerged tilted bell. It should be observed that the generation 

 of gas in the protojolasm of Amoeba and Arcella was observed thirty 

 years ago by Maximilian Perty, who gave the same explanation of the 

 phenomenon as Engelmann." 



Sperm-formation in Spongilla. — The presence of corpuscles of a 

 zoospermatic nature in Spongilla appeared, says Dr. C. Keller,f from 

 Lieberkiihn's researches in 1856 to establish as an assured fact the 

 existence of a sexual differentiation in the sponges. Since then, how- 

 ever, the investigation of marine sponges has so seldom succeeded in 

 showing the spermatic elements, that recently serious doubts have 

 been raised in influential quarters as to the sexual differentiation — 



* ' Zoologisclier Anzeiger,' vol. i. p. 248. f Ibid., p. 314. 



