174 E. H. HARPER. 



developed, a continuous band of fecal matter being visible 

 through the length of the worm. During rapid division another 

 zone of fission makes its appearance, one segment in front of the 

 one previously formed, making a chain of three zooids. 



This method of self-division is often compared with the more 

 primitive type called fragmentation in which the parts separate 

 before regenerating the ends. The physiological regeneration 

 that takes place in self-division is the same in its results as re- 

 generation from a cut surface. Asexual multiplication continues 

 through the warmer months. In October and November the 

 sexual organs attain maturity. Budding then ceases, and the 

 po\ver of regeneration is also diminished. 



METHODS. 



Whole mounts of these worms have been made by the follow- 

 ing method. As stated above, the results of this paper have 

 been obtained from the study of the living forms, but when it 

 has been desired to preserve specimens to show results of regen- 

 eration, difficulty was encountered in killing the animals in an 

 extended condition, since they invariably become coiled up on 

 application of the fixing fluid. A remedy for this was found by 

 getting the animal extended in the angle between the beveled 

 edge of a slide and a glass plate. A very little hot sublimate- 

 acetic applied to the animal in this position will be drawn under 

 the slide with considerable force and prevent, the animal from 

 moving. If as little liquid as possible be used, the animals may 

 be killed in a perfectly extended condition. The animal should 

 be placed on the glass plate in a small drop of water. If the 

 slide is then moved up to the drop, the worm will become ex- 

 tended next to the glass, and held there with sufficient force to 

 prevent its coiling when the killing fluid is applied. 



I. REGENERATION IN THE ASEXUAL FORMS. 



Experiments. i. A resume of some general features of re- 

 generation in Sty/aria. 



These forms including 5. laciistris have been studied exten- 

 sively, both in respect to their method of self-division and their 

 regeneration. Section within the middle region is followed by 



