102 Moll . 
MOLLUSCOIDE A . 
genera ; 7 were found in the North Atlantic, 5 in the South Atlantic, 18 in 
the Southern Ocean (to the south of the Indian Ocean, including Kerguelen), 
10 in the seas of the Malayan Archipelago, 6 in the North Pacific, 28 in the 
South Pacific, 12 near the southern end of America. It appears from these 
lists that simple Ascidians are not abundant in the northern hemisphere, 
and are comparatively scarce in tropical latitudes, while they attain their 
greatest numerical development in southern temperate regions, 33 species 
having been found between 30° and 40° S. lat., and 28 between 40° & 
45°. In Boltenia, one species occurs in the extreme north, while the other 
two are from far south, the genus being unrepresented in intermediate 
latitudes. Concerning the bathymetrical distribution, 47 species, repre- 
senting 13 genera and all 4 families, were found between the shore 
and 50 fath. ; 22 species (9 genera, 4 families) between 50 & 500 fath. ; 
8 species (5 genera, 3 families), between 500 and 1000 fath. ; G species, 
viz., Culeolus recumbens, perlucidus, perlatus , Fungulm cinereus , Bathy- 
oncus mirabilis ( Cynthiidce ), and Corynascidia suhmi (A scidiidce), between 
1000 & 2000 fath. ; and finally 7 species, viz., Culeolus murrayi , moseleyi, 
Styela bythia , squamosa ( Cynthiidce ), Coi'ynascidia suhmi , Abyssascidia 
wyvillii , and Hypobythius calycodes ( A scidiidce) between 2000 & 3000 
fath. The Cynthiidce and A scidiidce range from the shore to 2600 fath., 
the Molgulidce to GOO fath., the Claveliniclce only to 129 fath. The 
nature of the bottom and the temperature appear to have little influence 
upon their distribution. Many deep-water forms have the posterior end 
of the body prolonged to form a peduncle by which the animal is 
attached ; for example, Ascopera among the Molgulidce , the Boltenince , 
Corynascidia and Hypobythius among the A scidiidce. Tunicata of the 
‘ Challenger/ Geogr. Distrib. pp. 249-274, summary, p. 275. 
12 species of simple Ascidians, collected on the southern coasts of 
England during the cruise of the yatch ‘ Glimpse/ are enumerated and 
described by II. 0. Sorry & W. A. IIerdman, J. L. S. xvi. pp. 527-53G. 
West Indies and Brazil. 1 species of Molgula , 7 Cynthiidce , and 7 Phal- 
lusiidce described in Danish and Latin by P. A. Tkaustedt, Yid. Medd. 
1881, pp. 108-125 & 271-286, figures of. .the whole animals pi. iv., parti- 
culars of the branchial sacs, pi. v. 
Ascidijj simplices. 
P. A. Traustedt points out that some genera and species of Ascidians 
are asymmetrical : agreeing with Lacaze-Duthiers in calling the side of the 
ganglion dorsal, and the side of the intestine ventral, he finds that in the 
families Cynthiidce and Molgulidce , and in most species of Phallusia , except 
P. turcica (Sav.), the intestine deviates to the left, in Chelyosoma , Corella, 
Rhodosoma, and A byssascidia to the right. The disposition of the muscles 
is asymmetrical in Phallusia , Corella , Chelyosoma and Abyssascidia , the 
muscles of the right or left side being more developed, generally of that 
side which is opposed to the deviation of the intestine. The oral and 
cloacal orifices also become asymmetrical in Chelyosoma , that is to say, 
they are not contained in the median plane, which is determined by the 
ganglion, the basis of the dorsal plait, and the ventral furrow, but deviate 
