A FUETHEE STUDY OF THE DEVELOPMENT OF THE 

 EXCEETOEY OEGANS IN" BDELLOSTOMA STOUTI. 



BY 



GEO. C. PRICE, Ph. D., 



Associate Professor of Zoology, Iceland Stanford Jr. University. 



With 31 Text Figures. 



Much of the following work has been done in the Embryological 

 Laborator}^ of the Harvard Medical School, and it gives me great pleasure 

 to here acknowledge m}' many oliligations to the Director, Professor 

 Charles Sedgwick Minot, for his unvarying kindness and helpfulness. 

 I wish also to express my thanks to Professor Oscar Hertwig for his 

 kindness in placing the resources of his laboratory at my disposal during 

 a four months' residence in Berlin. 



In a previous paper on this subject ^ the excretory organs were described 

 in three stages, designated as A, B and C. Of these A showed the sys- 

 tem in an early though not in the earliest stage of development, B fol- 

 lowed quite closely upon A, but between B and C there was a wide gap, 

 the organs in C resembling in many respects those of the adult. 



A subsequent study of better material, and of a rather full series, 

 beginning with specimens younger than A and ending with others older 

 than C, has revealed certain errors both of observation and interpre- 

 tation, and has at the same time brought to light some new and inter- 

 esting facts. It is the object of the present paper briefly to present these 

 facts and to correct the errors. No attempt will be made to discuss the 

 morphology of the excretory organs of the vertebrates in general. 



It may be stated at the beginning that additional observations have 

 abundantly confirmed the main point of the previous paper, namely, that 

 in Bdellostoma the entire excretory system arises as a pronephros, and 

 that from this both the pronephros and mesonephros of the adult are 

 derived. 



In the previous work, on account of the difficulty of counting the 

 myotomes in transverse series, especially at the anterior end, recourse 



'Price, G. C: Development of the Excretory Organs of a Myxinoid, Bdel- 

 lostoma stouti. Zool. Jarb., Vol. 10, Anat., 1897. 



American .Tori:NAL of Anatomy. — Vol. IV. 



