E. './. Scrlpps. Six cruises, 3ach covcrinf^ a pattern of approxi- 

 mately forty stations, v/o-ro made during the spring and early suraraor of 

 each year. The region surveyed is. the area of maxnnum spavming of the 

 pilchard (Scofield, 193h) • It had as its northern limit the group of 

 islands of i.'hich Santa Cruz is the largest, and extended in the south 

 to near the Coronados Islands; the stations ranged fron near shore to 

 about 150 miles out to sea. The region covered and the pattern of sta- 

 tions occupied was somewhat different during the second season, but es- 

 sentially the sane area vras surveyed in both years. 



The racthods employed in the collection of plankton- samples contain- 

 ing pilchard eggs ■vfill be treated in detail in another paper devoted to 

 the results of the spawning surveys of the 3/cars 19U0 and I9I1.I. For the 

 purposes of the present article, it is sufficient to state that oblique 

 hauls were made I'/ith either a one-meter or tvro-meter net from approximately 

 75 meters deep to the surface, the hauls talcing, on the average, about 

 2i4. minutes of towing time. Stations v/ere occupied at whatever hour of 

 the day or night they were reached. Temperatures v/ere taken at each sta- 

 tion at 10-meter intervals in the upper ^0 motors of livater and at 25-nieter 

 intervals in the next 50 meters, with reversing thermometers attached 

 in pairs to Nansen vrater bottles. 



DESCRIPTION OF THE. PILCHARD EGG 



The pilchard egg can be readily identified by the follov;ing com- 

 bination of characters: a wide perivitelline space, a single oil globule, 

 and an irregularly segmented yolk. The eggs are spherical, with the 

 egg membrane thin, unsculptured, quite transparent, and v^-ith a bluish 

 or purplish cast. The egg membrane is easily broken, more so than those 

 of most planktonic eggs; in the plankton saraples studied it vms commonly, 

 absent from a third to a half of the eggs , probably having been broken 

 in the net, or in fractioning or sorting the material. Fertilized eggs 

 average about I.70 mm. in diameter (range 1.35 - 2.05 mm.). This is of 

 similar size to the fertilized egg of the European pilchard. The peri- 

 vitelline space is wide, having nearlj'' as great a width as the yolk mass. 

 Tfe have encountered no other pelagic fish egg of the size of the^pilchard 

 egg in the area investigated that are so characterized. The yellovfis'h- 

 brown yolk appears to be made up of a- number of irregular cells,, but it 

 is composed of a large number pf separate particles of yolk material closely 

 pressed together. There is a single oil globule, O.I6 mm, in diameter. 



In connection •with these studies the development of the pilchard egg 

 was separated, on the basis of readily observable morphological character, 

 into eleven stages v;-hich are jiot of equal time duration. A brief descrip- 

 tion of each stage is given- in the appendix (p. 9 ). 



134 



