CATALOGUE OF TUNICATA. 59 



and possibly the following species insufficiently described by Quoy and 

 Gaimard : Ascidia reticulata, A. tumulus, and A. sabulosa, from Port 

 Western. 



Sub-order II. ASCIDIA COMPOSITE, 



Savigny, 1816. 



This group contains fixed Ascidians, which reproduce by 

 gemmation so as to form colonies in which the Ascidio- 

 zooids are buried in a common investing mass, and have 

 no separate tests. 



It is now agreed by all authorities that this is, in all 

 probability, a polyphyletic group, the Compound Ascidians 

 having been derived from several distinct groups of ancestral 

 Simple Ascidians. They are thus a semi-artificial assem- 

 blage consisting of those fixed Ascidians which have 

 retained or acquired the power of reproducing by gemmation, 

 so as to form colonies, and in which the Ascidiozooids 

 have remained so intimately united that their tests form a 

 common colonial mass. 



Some zoologists, such as Lahille, Garstang and Sluiter, 

 would break up this group at once, and scatter its con- 

 stituents amongst the families of Simple Ascidians ; but I 

 am supported by Seeliger, Hitter and others in thinking 

 that such a course would be premature, that the colonial 

 form and common test, whether acquired independently or 

 not, represent a community of structure which ought to be 

 expressed in our classification, that we may get further 

 light upon genetic affinities when the method of budding 

 is known in many more genera, and that, consequently, it is 

 a practical convenience to retain for the present the group 

 Ascidiae Composite. 



The seven families of Compound Ascidians may, however, 

 be arranged in two well-marked groups to which Sluiter's 



