180 ARTHUR DENDY. 



system is met with in species with very distinct types of 

 skeletal arrangement (as will be seen subsequently), cause me 

 to believe that it is of no value for systematic purposes, although 

 it is of great interest, as probably representing a late stage in 

 the evolution of the Leuconoid from the Syconoid type of 

 canal system by branching of the radial chambers and restric- 

 tion of the collared cells to the branches. (It is also conceiv- 

 able that the Sylleibid type may have originated from the 

 Syconoid by folding of the wall of the gastral cavity, but there 

 is very little evidence in favour of this view; while, in some 

 species of Sycon and Grantia, we have a certain amount of 

 evidence, in the arrangement of the skeleton, for believing in 

 the direct conversion of flagellated chambers into exhalant 

 canals. That both processes may have taken place together I 

 do not for a moment deny.) 



In some species of Leucandra we find, as in the case of 

 Synute pulchella, a very strong tendency towards the forma- 

 tion of massive, irregular colonies, by the more or less com- 

 plete fusion of a number of Leuconoid individuals. Hence we 

 find species which, instead of having a single well-defined 

 central gastral cavity, with a single terminal osculum and a 

 correspondingly definite sac-shaped external form, as in Leu- 

 candra phillipensis, exhibit an irregular massive form with 

 a larger or smaller number ofoscula scattered over the surface, 

 each osculum being the outlet of a wide exhalant canal, which 

 probably corresponds to the gastral cavity of a single Leu- 

 conoid individual. Synute pulchella is of great interest 

 as showing us how such forms have probably arisen. As far 

 as my experience goes, all such massive colonial species have 

 in other respects a typical Leuconoid canal system with small 

 rounded chambers, as in the Australian L. gladiator (4). 



Lelapia. 

 The canal system of this remarkable genus is unfortunately 

 unknown, but from the fact that Mr. Carter (12), who has 

 personally studied it, places it amongst the '' Leucones,^^ it 

 seems probable that it conforms to the Leuconoid type. 



