No. 2.] STOLONIZATION IN AUTOLYTUS VARIANS. 293 



epidermis is entirely obscured. Posterior to and over the 

 median tentacle, as well as over the other tentacles, the epi- 

 dermis is present as a distinct layer of tissue ; but where the 

 base of the tentacle encroaches upon cortical tissues the outline 

 of this layer becomes abruptly lost, and in regions anterior to 

 this tentacle the cortical substance seems to be composed of 

 cells of uniform structure, and to extend from the medullary 

 substance to the borders of the cuticle without presenting even 

 a peripheral line of nuclei to indicate the presence of such a 

 layer. This intimate association of cortical and epidermal cells 

 was first pointed out by Fraipont (12) in Protodrilus, and it 

 appears to be a condition common to all Syllidians. In 

 sections of the head of Autolytus pictus and Eusyllis there 

 exists, according to Malaquin (9), a peripheral arrangement 

 of cells, by the orientation of which he is able to recognize 

 an epidermal layer. Such an arrangement of cells is not 

 sufficiently apparent to justify the recognition of a distinct 

 epidermal layer in a section of the head of a mature stolon of 

 Autolytus varians ; and in a similar section of the head of the 

 parent stock the orientation, while being more evident, is not 

 sufficiently marked to indicate the presence of a true epidermis. 

 What results are to be obtained in the distinguishing of these 

 two structures by the employment of special methods, hitherto 

 not tried, I shall endeavor to demonstrate in a later paper. 



The internal structures of the head of the parent stock are 

 so similar in character and arrangement to those of the stolon 

 that it would be useless to repeat the figure. The medullary 

 substance of both are alike in size and divisions into lobes, 

 while the arrangement of ganglion cells into centers is as well 

 marked in one as in the other, and the only way by which a 

 section of the adult head might be distinguished from a similar 

 section of the head of a mature stolon would be by differences 

 in the alimentary canal, the increase in size of the median ten- 

 tacle, and the absence posterior to the median tentacle of a 

 ciliated region known in species of Autolytus where this is 

 more marked as the epaulets. Thus it is evident that as far 

 as internal structures are concerned, the head of the stolon is 

 an exact reproduction of the head of the parent stock, and the 



