TUN1CATA. 
Moll. 101 
together, the male duct (canalis deferens), when filled with spermatozoids, 
presses on the female duct, and obstructs the exit of the eggs, so that 
both are evacuated about the same time. The formation of the sperma- 
tozoids is also described. C. R. xciv. pp. 1726-1729. 
J. Playfair McMurricii has observed in Ascidia and Cynthia that 
the so-called test cells have their origin in the yelk, and migrate from 
thence outwards in the space surrounded by the egg-membrane ; they 
contain neither nucleus nor membrane, but only 2-3 granula of yelk- 
substance, and cannot be distinguished from particles of eggs which have 
been crushed and dilacerated by external pressure : Stud. Biol. Lab. 
Hopkins Univ. ii. p. 147, pi. x. ; abstract in Biol. Centralbl. 1882, pp. 620 
& 621, and in Arch. Z. expcr. x. p. lxii. 
O. Seeliger describes the formation of the eggs within the ovary in 
individuals of Clavelina Icpadiformis ( L.), its migration into the peri- 
branchial space, where it becomes fecundated, and the first formation of 
the buds in the same species, comparing his results with those of previous 
authors on tho same subject ; thero is not auy analogy botween the pro- 
cess of gemmation and tho development in the egg and tho larval stages; 
gemmation is therefore probably a very lately acquired faculty ; the 
author did not succeed in observing the formation of eggs in individuals 
raised from the egg or from the free larval stage, but only in individuals 
formed by gemmation, and he supposes therefore that the former are not 
able to produce eggs. SB. Ak. Wien, lxxxv. Abth i. pp. 361-413, 3 pis. 
Popular description of the metamorphosis of the Tunicata by O. 
Tasciienberg, Verwandlungen der Thiere, 1882, pp. 149-152, with a 
woodcut. 
Herdman, l. c. p. 25, proposes the following classification of the 
Tunicata : — 
Order i. — A scidiacea. 
Sub-Order i. Ascidicc simplices. 
Family 1. Molgulidce ; 2. Cyntliiidce (including as subfamilies 
the Boltcnincc and Styclince ); 3. Ascidiidcc ; 4. Clavelinidce. 
Sub -Order II. Ascidice composite. 
Family 1. Botryllidce\ 2. Didcmnidce ; 3. Distomidcc ; 4 .Polycli- 
nidcc ; 5. Diplosomiclce. 
Sub- Order in. Ascidicc salpiformes. 
Family, Pyrosomidcc. 
Order n. Tiialiacea. 
Family 1. Doliolidm ; 2. Salpidcc. 
Order hi. Larvacea. 
F amily , Appendiculariidcc. 
Geographical Distribution. 
Herdman has worked up the simple Ascidians of the ‘ Challenger } Expe- 
dition, describing and figuring 82 species, most of which were not known 
before, but have been preliminarily characterized by the same author in 
P. R. Soc. Edinb. 1879-81; some are entirely new, including some new 
