vol i i Eitter-Davis.— Enteropneusta. 201 



therefore, extends over a period of at least four months. 

 Attempts were made at various times to artificially fertilize the 

 eggs but with no success. In spite of careful search for fertilized 

 eggs and developing embryos during each breeding season for 

 several years, none were found until November 15, 1902. At 

 that time, on examining a burrow containing a mature female, 

 about twenty young embryos, some unhatched and some free, 

 were found. Doubtless the failure of previous years was due to 

 attempting to find the eggs in the sand instead of carefully 

 looking for them in the burrows of females. Sickness prevented 

 further search at this time. A little later the entire mud flat 

 over which the animals were distributed was covered by the 

 dredging operations prosecuted in connection with the harbor 

 improvements at San Pedro. This destruction of collecting 

 grounds has made it impossible, so far, to complete the series of 

 stages necessary for a detailed study. Keenly appreciating the 

 importance of such a study we hope to obtain sufficient material 

 at San Diego to carry it out at some future time. 



Among the specimens secured were a few stages of develop- 

 ment from the late gastrula where the ciliary band was present 

 to beyond the formation of the collar. The observations we 

 were able to make, limited chiefly to the external features, 

 confirm the only recorded description of direct development 

 of Enteropneusta, Bateson, '84, in all important particulars 

 except one: The neural fold makes its appearance later than in 

 />'. kowalevshii. A few points of minor importance may be added. 

 The first groove, the anterior, of the collar of the embryo becomes 

 distinct in three hours after the first trace of its appearance. 

 The second groove, completing the collar, appears about fifteen 

 hours later. The width of the collar when first formed is 

 .016 mm., the length of the' embryo at this time being .127 mm. 

 The tuft of large bristle-like cilia at the end of the proboscis 

 makes its appearance about the time the second groove is fully 

 formed and before the embryo escapes from the egg. Animals 

 do not swim freely but glide about with proboscis pointed forward 

 over the supporting surface. These movements arc made mainly 

 by means of the large cilia composing the posterior ciliary band 

 although their action ceases occasionally for short periods. At 



