324 RANDOLPH. [Vol. VII. 



"3, dieser Chordazellenstrang ist continuirlich durch alle 

 Schnitte hindurch zu verfolgen, welche noch embryonalen 

 Charakter tragen, und er liegt hart unter den beiden Nerven- 

 strangen des centralen Nervensystems ; 



"4. die Muskelblatter wachsen gleichzeitig von zwei der Axe 

 des Korpers entsprechenden Linien aus neural- und cardial- 

 warts, genau wie bei Wirbelthieren ; es wird somit 



" 5. durch diese Vorgange eine Axe auch in Anneliden be- 

 zeichnet von welcher nach unten bin sich das aniraale, nach 

 oben hin das vegetative Rohr schliesst. 



" Es ist endHch 



" 6. sehr vvahrscheinlich — obgleich ich es bis jetzt nicht vollig 

 ausser Zweifel stellen konnte — dass das gesammte Mesoderm 

 mit Einschluss der Darmfaserplatte aus dem Ectoderm her- 

 stammt." 



Thus the chorda cells are to be considered as arising together 

 with the rest of the mesoderm from the ectoderm. 



Biilow notices the presence of the chorda cells, but gives no 

 other explanation of their meaning. 



In my view, however, it is from these large cells that the 

 greater part of the mesoderm is regenerated, and they do not 

 arise from the ectoderm but are present in the mesoderm of the 

 adult individual. On closer examination they are found to be 

 limited to a definite tract of the peritoneum and to extend 

 throughout the greater part if not the entire extent of the 

 worm. Their position and aspect are shown in Fig. i. They 

 lie along the free surface of the ventral longitudinal muscles, on 

 each side of the ventral nerve cord, between it and the ventral 

 setae. The nuclei are round or oval in section, granular, and 

 possessing large and deeply staining nucleoli ; they are sur- 

 rounded by cell bodies of irregular form, which stain more 

 deeply than the adjacent protoplasm. These large cells, for 

 which I have proposed the name neoblasts, are distinguishable 

 from the remaining cells of the peritoneum by their great size 

 and by the presence of a cell body, which I have not been able 

 to discover in the case of the ordinary peritoneal cells. The neo- 

 blasts are to be found in every somite (Fig. 2), with the excep- 

 tion of perhaps one or more at the anterior extremity ; and, on 

 the separation of the worm into parts, the one or more present 

 in the end somite soon begins to divide. I have traced the 



