PLASMA-STRUCTURE IN EGG OF HYDRACTINIA 193 



latter. Since Hydractinia echinata shows both mitochondria 

 and protoplasmic granules which take 'nuclear' stains, it forms a 

 favorable object for study of the origin and relation of these 

 elements, the results of which form the first portion of the paper. 

 In a second part a few observations are briefly presented which 

 are intended to supplement previous descriptions of matura- 

 tion and fertilization in Hydractinia echinata and Eudendrium 

 ramosum. 



This investigation was undertaken at the suggestion of Prof. 

 E. B. Wilson, to whom I wish to express sincere thanks for his 

 kindly direction of the work. For suggestions concerning certain 

 experimental aspects of the problem I am indebted to Prof. T. H, 

 Morgan. I wish also to express my thanks to Prof. F. R. Lillie 

 for his generosity in putting a room at my disposal during several 

 summers at the Marine Biological Laboratory at Woods Hole. 



III. PROTOPLASMIC GRANULES AND MITOCHONDRIA IN 

 HYDRACTINIA 



A. MATERIAL AND METHOD 



The material for this work was obtained at Woods Hole during 

 the summers of 1910, 1911 and 1912. The egg of Hydractinia 

 is very favorable for staining tests, since all stages of development, 

 from the early egg in the entoderm to the mature egg in the gono- 

 phore, are present on the same stalk, making it certain in staining 

 tests that all stages receive the same treatment. Since a change 

 in staining reaction occurs during development of the egg, this 

 is of much importance. One possible difficulty with this material 

 is the well-known fact that the nucleus early loses its affinity for 

 basic stains and may take acid stains but slightly. If care be 

 used in determining the staining reaction of the chromatin in the 

 very early stages, no confusion need result from this condition. 



Various killing fluids were used, the results of which for the 

 sake of brevity and clearness have been tabulated (table 1). 

 Material fixed in fluids containing chromic and osmic acids is 

 best for the study of both nucleus and protoplasm, since the 

 integrity of the elements is much better preserved than in other 



