EEPOKT ON THE TUNICATA. 
149 
PoLTCIilNID^, 
Genus. 
ApUdium. 
PdlycUnum. 
Subgenus. 
ApUdium. 
Amaroucium. 
J Fragarium. 
j Circinalium. 
Morcliellium. 
_ Sidnyum (]). 
( Polyclinum. 
< Aurantium. 
( Sidnyum (?). 
It is not very clear whether he regards Sidnyum as coming under the genus ApUdium 
or the genus Polyclinum, and he does not state where he places Synoicum. 
Von Drasche, writing in 1883, virtually endorses Giard’s classification. He accepts 
the two main generic types ApUdium and Polyclinum, places Sidnyum, Synoicum, and 
Sigillina as subgenera under ApUdium, and recognises no subdivision in Polyclinum. The 
restoration of Sigillina to the Polyclinidse constituted, however, a distinct advance upon 
Giard’s scheme. Later on in the same year von Drasche^ founded a new subgenus 
of ApUdium, Polyclinoides, for a species from Mauritius. The affinities of this form will 
be discussed further on. 
YerriU’s Macroclinum'^ seems not to be sufficiently distinct to require a separate 
genus. It contains a single species, MacrocUnum crater, Verrill, from the Banks of 
Newfoundland. More information in regard to this form is required before, it can be 
referred with certainty to its proper position. 
The shape of the colony in this family is exceedingly varied. It is usually irregular 
and massive, and is frequently lobed on the upper surface. In some cases {e.g., Pharyngo- 
dictyon mirahile, PL XXL figs. 1, 2, 3) the lower part of the colony next to the point of 
attachment becomes prolonged to form a peduncle ; while in others {e.g., Psammaplidium 
effrenatum) the colony becomes flattened and forms a thin incrusting layer. It is com- 
paratively rare amongst the Polyclinidse to find the systems conspicuous and distinctly 
circumscribed as they are in the Botryllidae. In most cases they are so irregular that it is 
impossible to make out their limits in specimens preserved in alcohol, and very generally 
the common cloacal apertures if present are not visible. It was this circumstance which 
led to the establishment of Amaroucium as a generic name (see under Amaroucium, 
below). 
The Ascidiozooids of the Polyclinidse are very characteristic. They are usually of 
large size, and are greatly elongated antero-posteriorly. The intestinal loop extends for 
a considerable distance behind the branchial sac, forming the region distinguished by 
Milne-Edwards as “ abdomen,” but the length of the body is in most cases mainly due to 
the long “ post-abdomen,” which extends behind the intestinal loop and contains the 
1 Uebereine neue Synascidie, Verhandl. d. Ic. k. zool.-hot. Gesellsch. Wien, Ed. xxxiii. p. 119. 
^ Amer. Journ. Sci. and Arts, 3rd series, vol. i. No. 4, p. 288, 1871. 
