126 



R. P. COWLES. 



Fig.l 



FIG. I . Larva of P. appendi- 

 ciilatits, X 68. 



the seemingly rapid metamorphosis of the larva into the adult 

 form and also it shows why the young worm immediately after 

 metamorphosis is so much longer than the fully developed larva. 



The anal segment is of specific in- 

 terest in the larva (Fig. i) which is 

 found at Beaufort, N. C, because it 

 bears the beginnings of two anal fila- 

 ments which are characteristic of the 

 larva of Polygordius appendiculatus. 

 Besides these organs there is on the 

 anal segment a tuft of cilia about the 

 anus. Anterior to the anal filaments 

 there is a ring of glandular papillae. 

 A pre-anal ring of cilia was not ob- 

 served. 



At the suggestion of Dr. Grave, of 



the Johns Hopkins University, the 

 young worms, after the completion 

 of metamorphosis, were put into 

 dishes with water and sand rich in diatoms. In order to ob- 

 tain sufficiently rich cultures of diatoms to afford enough 

 food for the worms, sand was obtained by means of a dredge 

 outside of the harbor and put into aquaria jars with fresh 

 sea water. The jars were then kept in the laboratory near a 

 window until the sand had settled and a rich culture of diatoms 

 had appeared as .a brown layer on the top of the sand. This was 

 then drawn off with a pipette and fed to the young worms. Under 

 these conditions they grew rapidly and at the end of six weeks 

 some of them had increased in length to i 5 mm. Examination 

 of the contents of the alimentary canal showed that the worms 

 had been feeding on the diatoms. 



This method of rearing the young metamorphosed larvae was 

 first employed by Grave to rear young Echinoderms. By this 

 method also the writer has had good success in rearing the larvae 

 of Thalasseina taken from the tow^at Beaufort, N. C., and he has 

 half-grown specimens of Thalassema which are living and grow- 

 ing under these conditions in the laboratory of Johns Hopkins 

 University. 



