NO. 4 HARTMAN : SPIONIDAE FROM CALIFORNIA 301 



adults with developing stages are obtainable. They are tolerant to condi- 

 tions in the laboratory and may be kept alive for weeks in small dishes. 

 The translucency of the cocoon permits observation of activities within. 

 Eggs are deposited in soft, capsulelike cocoons (pi. 47, fig. 33). They are 

 spherical in shape, opaque, yellow, measuring 0.12 to 0.15 mm in diameter 

 and number 20 to 80 in a cocoon. Size of eggs and cocoons varies directly 

 with that of the adult depositing them. Fifteen to 20 or more cocoons 

 are deposited within the loosely constructed tube of an adult, approxi- 

 mately in linear series ; each cocoon is attached to the tube (pi. 46, fig. 28) 

 by a double stalk. 



Soderstrom ( 1920, pp. 185-191 ) has given the most plausible explana- 

 tion of the manner of egg deposition and cocoon building as it is known to 

 occur among some members of the Spionidae. His observations and con- 

 clusions were based on Pygospio elegans Claparede and 2 species of Poly- 

 dora. Since these views are in striking contrast to others that have been 

 forwarded by Whitlegge, Mesnil and Caullery, and others (see Soder- 

 strom, 1920, p. 185), they are briefly summarized. Soderstrom maintains 

 that the rim of the nephridial pores secretes the material making up the 

 capsular membranes, and that the eggs (which sometimes measure con- 

 siderably more than the diameter of the nephridial aperture at the time of 

 egg laying) literally flow through the nephridial tube and only take their 

 definitive form in the capsule. At the time of egg laying, the body of the 

 adult is pressed close against the wall of the tube. A secretion emerges 

 from a pair of nephridial pores of a particular segment and is applied to 

 the wall of the tube until a pair of short stalks results. This substance is 

 sticky when shed but does not adhere to the eggs. When the eggs are 

 extruded, they cause the walls of the elastic membrane to extend, such 

 that its inner walls merge, resulting in a single vesicular sack (pi. 46, fig. 

 27). Thus, eggs emerging from both nephridial pores at the same time 

 come to occupy the same capsule. The free distal end of a cocoon termi- 

 nates the process and may show a small papillar elevation on either side, 

 or it may be evenly rounded (as in B. proboscidea) . The end of the proc- 

 ess is diagrammatically shown in pi. 46, fig. 27. 



The fertilized egg gives rise to a smooth, spherical, opaque blastula. 

 If development is allowed to proceed normally (in the absence of canni- 

 balism), a weakly ciliated, nearly spherical, modified trochophore devel- 

 ops. The cephalic region is identifiable by a pair of clear spots at the 

 anterior end (pi. 47, fig. 30). In many cocoons development of all zygotes 

 seemingly proceeds at such tempo that all embryos are in about the same 



