NOTES AND MEMORANDA. 179 



Fig. 10 results (a form abnormal in Plectronella, freq[uent among the 

 Hexactinellidai). 



Fig. 11 requires no comment. 



Fig. 13 is the result of a sexradiate growth, of the cell along three 

 axes at right angles to each other, and represents the typical Hexac- 

 tinellid spicule. 



Fig. 14 is an octoradiate form, seven buds having grown out 

 radiately in one plane and the eighth at right angles to them ; it 

 occurs in the fossil Hyalostelia. 



The foregoing remarks arose out of the description of Plectronella 

 papulosa, which was the main object of the paper ; but the variability 

 of sponge-spicules, Mr. Sollas points out, is far too important a subject 

 to be treated thus incidentally, and might furnish material enough for 

 a lengthy memoir. No sj)onge that has come under his observation 

 has failed to exhibit numbers of spicules departing more or less 

 widely from the average type ; frequently the range of variability is 

 extreme ; and no doubt, when a large number of specimens of allied 

 species of sponges come to be carefully compared, we shall find not 

 only in their external form, but in the details of their internal struc- 

 ture as well, easy j)assages from one to the other, and links will be 

 discovered uniting together types of sponge-structure that now appear 

 widely separated from one another. 



Gloidium, a new genus of Protista. — This genus, recently dis- 

 covered by Dr. N. Sorokin, of Kasan,* differs in many respects from 

 any of the hitherto known forms of Protista. It is a minute myxopod 

 ( • 03 mm. in diameter), with short, blunt pseudopodia, and protoplasm 

 distinctly differentiated into a clear transparent ectosarc, and a 

 frothy-looking endosarc containing reddish or j^ellowish granules. 

 There is no nucleus, but a large contractile vesicle in the ectosarc, 

 contracting about every three or four minutes. 



Multiplication takes place by division, the process being a some- 

 what singular one. Constrictions appear in the protoplasm at the 

 opposite poles, and soon after two similar constrictions, the plane of 

 the second division being at right angles to that of the first. Then 

 the pairs of constrictions deepen, extending nearer and nearer to the 

 centre, until, at last, four masses are produced, united to one another by 

 as many delicate threads of protoplasm proceeding from a common 

 point : finally, the four masses become free. At first there is a single 

 contractile vesicle in the centre of the dividing mass, but as division 

 goes on, each mass is provided with a pulsating organ. 



The author failed to see any food particles in the endosarc, and 

 supposes that the organism is nourished entirely by imbibition. It 

 is, therefore, devoid of one of the most constant animal characteristics 

 — the power of ingesting solid nutriment. 



Under certain circumstances not well understood, encystation 

 takes place. A thin, scarcely noticeable investment is formed by the 

 hardening of the superficial layer of ectosarc. Fresh layers are found 

 in the same way, until a laminated cyst is produced. At one spot all 



* ' Morphologiscbes JabrLuch,' vol. iv. (1878). 



