THE COMMISSURES AND THE NEUROCORD CELLS 

 OF THE BRAIN OF CEREBRATULUS LACTEUS. 



BY 



CAROLINE BURLING THOMPSON. 



With Thirteen Figures. 



1. Introduction 641 



2. Methods 641 



3. The commissures 642 



a. Historical review 642 



h. The commissures of Cerebratulus lacteus 643 



4. Neurocord Cells 650 



a. Historical review 650 



h. The neurocord cells of Cerebratulus lacteus 652 



5. Conclusions and summary 654 



6. Bibliography 656 



7. Figures 657 



I. INTRODUCTION. 



The material for this paper was obtained partly at Sea Isle 

 City, N. J., during a collecting trip under the direction of Dr. 

 E. G. CoNKLiN and Dr. T. H. Montgomery, Jr., and partly near 

 Wood's Hole, Mass. To both Dr. Conklin and Dr. Montgomery 

 I am indebted for the suggestion that the nervous system of this 

 nemertean should be worked over. The material was sectioned 

 and mounted in the Biological Laboratory of the University of 

 Pennsylvania, and was then laid aside until the present time, but 

 it is a pleasure to recall the kindness and the many helpful sug- 

 gestions which I received in Dr. Conklin's laboratory. 



2. METHODS. 



Two very large worms were dug up in a small inlet running 

 back from the sea above Sea Isle City. One was fixed in Kosta- 

 necki's Fluid, the other in 95 per cent alcohol. The former did 

 not give satisfactory results, owing to the gerat shrinkage both 

 of the body as a whole and of the individual tissues, but the worm 

 fixed in 95 per cent alcohol was well extended, and all the tis- 

 sues were in excellent condition. Flemming's Fluid was tried for 



