474 University of California Publications in Zoology [Vol.16 



stratum. Budding abundant in some colonies. (See section on this 

 subject at end of description.) 



Period of egg-procluction. — January. 



Period of budding. — July. 



Habitat and distribution. — Under sides of rocks in the littoral zone 

 at La Jolla and in the San Diego region ; Dredging Station II off San 

 Pedro, depth six meters. 



Type locality. — La Jolla, California. 



This species seems to resemble Tridideninum {Didenmiim) strangu- 

 latum Ritt. as closely as any other but is well separated from it by 

 the shorter stigmata, unlobed atrial orifice, and presence of the mus- 

 cular process at the posterior end of the branchial sac. 



We are glad to name this species, a study of the budding of which 

 has received considerable of our attention, after Professor Delia Valle, 

 whose work on budding in this group is distinguished. 



The budding is very similar in this species to that described later 

 on in detail for Diplosoma pizoni. As seen in plate 44, figure 54, the 

 budded intestinal loop grows out just beneath the recto-esophageal 

 collar from two sources, the mother esophagi;s and the mother rectum. 

 Likewise the budded tliorax is connected to the same two sources of the 

 mother zooid posterior to the budded intestinal loop. The supposition 

 that a division takes place so as to give the mother thorax the newly 

 budded intestinal loop and the budded thorax the old intestinal loop 

 is supported by the fact that many zooids were seen with large 

 thoraces and small intestinal loops and vice versa. 



Diplosoma pizoni, n. sp. 



PI. 43, figs. 50 and 51; pi. 45, figs. 66 to 68 



Superficial characteristics of the colony. — Exceptionally soft, en- 

 crusting, several centimeters in expanse ; thickness about 3 mm. Color 

 of pi-e.served specimen mottled light and dark gray; closely set zooids 

 easily seen through transparent test. Common cloacal orificejs few in 

 nmnber, large and chimney-shaped. Each zooid surrounded by thin 

 layer of test and joined to lower surface of colony by a strand of 

 about the same length as zooid. The test consisting of upper and lower 

 thin layers, and strands surrounding zooids joining these layers, con- 

 taining great spaces between and among zooids ; many small color- 

 less cells and fewer but much larger round pigmented cells ; but no 

 bladder cells. 



Zooids. — About 1.5 nun. long. eon.sisting of thorax and abdomen. 

 Mantle containing much dark pigment especially over stomach and 

 intestine, the epithelial layer here consisting of large, flat, polygonal 

 cells with small, round, clear nuclei usually near one end of darkly 

 pigmented cell body (pi. 43, figs. 50, 51) ; adheres closely to surround- 



