484 University of California Public-ations in Zoology [Vol.16 



in length ; consisting of thorax, abdomen, and postabdomen, marked 

 off from each other by slight constrictions ; thorax and abdomen 

 usuall.v about same length. Musculature consisting of about fifteen 

 longitudinal muscle bands on a side, extending into postabdomen where 

 they are closer together and stronger; usually considerable pigment 

 in mantle. 



Branchial system. — Branchial orifice with six well-developed lobes; 

 atrial without lobes, but having a long, tapering, pointed languet. 

 Branchial sac with eight to fourteen series of stigmata, ten seemingly 

 most conmion; about twelve stigmata in a half-series. Endostyle 

 narrow and .straight. Dorsal langiiets, one to each transverse vessel, 

 placed to left of a clear strip of sac free from stigmata ; about as long 

 as stigmata and gradually increasing in length toward posterior end 

 of series. Branchial tentacles short, blunt, about ten, somewhat 

 irregularly scattered. 



Digestive system. — Plane of intestinal loop transverse to median 

 plane of zooid; esophagus large and almost twice the length of 

 stomach ; .stomach cylindrical, about as wide as long, with longitudinal 

 folds each presenting a loop turned toward anterior end of stomach ; 

 folds sometimes branching or discontinuous, making the number 

 variable for different colonies, twenty-two and fourteen being the 

 average for a large number of zooids. Intestine divided into three 

 divisions : anus not quite halfway up branchial .sac. 



Postabdomen and reproductive system. — Va^^■ing greatly in length, 

 short in young zooids. Testicular lobes (t., pi. 46, fig. 72) in two rows, 

 right and left. Ovary situated a short distance behind intestinal loop 

 .just anterior to testicular lobes, much less voluminous than the latter. 

 Larvae retained in atrial chamber till a late stage of development. 



Breeding season. — June and July, at lea.st. 



Habitat and distribution. — A. californicnm is probably the most 

 common ascidian on the California coast. It occurs on rocks, usually 

 on the under sides, at all points where collecting has been done, and 

 is found everjTvhere on piles, floats, breakwaters, etc.. except in the 

 upper portions of bays where the density and temperature of the 

 water are distinctl.v different from normal sea water. Dredgings do 

 not indicate that it flourishes in depths beyond a very few fathoms. 

 It also occurs at Puget Sound (Ritter. 1900). and. with some doubt, 

 on the Alaskan coast as far to the north and west as the Shumagin 

 Islands (Ritter. 1901). 



Type locality. — San Diego. 



Although A. californicum possesses no strikingly distinctive char- 

 acteristics, is very variable and has a wide distribution, it cannot 

 be identified with any hitherto described species. Its close.st relative 

 appears to be A. glabrum Verrill of the north Atlantic coast of North 

 America. The detailed examination of A. glabrum and also of the 

 allied species A. peUucidum by Van Name (1910) enables us to make 

 a pretty satisfactory comparison of californicum with these species. 



To the general form of the colony of californicum. the reverse of 



