148 
THE VOYAGE OF H.M.S. CHALLENGER. 
Family III. Polyclinid^. 
Colony usually massive ; sometimes iucrusting, sometimes lobed, or even 
pedunculated. 
Systems of various shapes, sometimes very irregular or absent. Common cloacal 
apertures usually inconspicuous. 
Ascidiozooids always elongated antero-posteriorly, and usually divided into three 
distinct regions. 
Test gelatinous or cartilaginous, sometimes rendered stiff by imbedded sand- 
grains. 
Branchial Sac usually small, and not highly developed. Stigmata usually small. 
Dorsal Lamina represented by a series of languets. 
Tentacles generally small and not numerous. 
Alimentary Canal extending considerably beyond the branchial sac posteriorly. 
Beproductive Organs placed behind the intestinal loop. Testis represented by a 
number of small spermatic vesicles attached to a large vas deferens. 
Gemmation from the post-abdomen. 
This large family, including an immense number of species, was founded by Giard in 
1872. It includes five of Savigny’s genera, viz., Aplidium, Polyclinum, Sidnyum, 
Synoicum, and Sigillina, all of which may still be retained either as genera or subgenera. 
Milne-Edwards in 1841 recognised that these forms, to which he added a sixth, 
Amaroucium, composed a natural group characterised by the shape of the Ascidiozooid. 
They constitute his 1’'® tribu, Polycliniens, which is practically, after the removal of the 
genus Sigillina, Giard’s family Polyclinidse. Milne-Edwards’ Amaroucium is probably, 
as Giard suggests, the same as Savigny’s Aplidium, Milne-Edwards having had the 
advantage of working at living material discovered the common cloacal apertures which 
Savigny who examined preserved specimens only had regarded as being absent. 
Alder in 1863 employed the genus Parascidia (which had been previously suggested 
by Milne-Edwards) for the reception of three species resembling Sidnyum in all points 
except that they have an eight-lobed in place of a six-lobed branchial aperture. This 
genus has not been recognised or discussed by any subsequent writer. Its relations to 
Circinalium and Fragarium, afterwards founded by Giard (see below), must be very 
intimate. 
Giard in 1872 formally raised the Polyclinidse to the rank of a family, from which, 
however, he excluded Sigillina, a retrograde step, since that genus is certainly more nearly 
allied to Polyclinum than to any of the Distomidse. Giard added a number of new 
species to the family, and established as new genera or subgenera Fragarium, Cir- 
cinalium, and Morchellium. His classification of the family appears to be as follows: — 
