174 J- THOMAS PATTERSON. 



case of polyembryony. It was this suggestion that induced me 

 to undertake a study of certain phases of the development of 

 Graffi.Ua; and this not only because of my interest in the general 

 subject of polyembryony, but also for the reason that an oppor- 

 tunity seemed to be offered to work out the details of this peculiar 

 phenomenon. Furthermore, if a true gemelliparous develop- 

 ment really did exist in so simple a fashion in a relatively low 

 organism like Graffilla, it might be possible to modify experi- 

 mentally the process and thus to be able to get at some of the 

 factors underlying it. 



While the results obtained from these studies have proved dis- 

 appointing, at least so far as the main object for which the in- 

 vestigation was undertaken, yet they are of a character such as 

 to warrant record, especially as they answer satisfactorily some of 

 the questions raised above. Furthermore, we have as yet only a 

 very few papers dealing with the development of rhabdocceles, 

 and consequently there is need of contributions along this line. 

 Methods. Various methods for preserving the material have 

 been used, but the most successful fixing fluid has been found to 

 be Benda's modification of Flcmming's strong solution. Speci- 

 mens fixed for two hours in this fluid give beautiful results for 

 cytological study, especially when followed by iron-haematoxylin 

 stains. Bouin's fluid also gave good preparations, but is much 

 less certain in its results. In making whole mounts the speci- 

 mens are placed under slight pressure and killed over a gentle 

 flame, and then fixed in a corrosive-sublimate solution. If 

 followed by borax carmine such material gives very clear figures 

 of many structures. However, I find the same "indefiniteness" 

 I about the reproductive organs as noted by Linton, especially in 

 | regard to the ducts, so that one can not rely upon mounts for 

 ' one's interpretation of the conditions of these structures. 



Notes on the Habits. Linton states that G. gemeUipara lives 

 on the gills of Modiolits, but there is some evidence that they 

 inhabit the kidney. This is brought out in the following experi- 

 ment. Two dozen specimens of Modiolus from a lot yielding no 

 Graffilloe from the gills were opened, care being taken not to injure 

 any of the tissues, and thoroughly washed out in water. No 

 parasite was found. The kidneys of these same individuals 



