no DAVENPORT ACADEMY OF SCIENCES. 



CARCHESIUM POI.YPINUM lyilltl. 



Bodies somewhat pyriform, the anterior border dilated. An 

 erect common pedicle, bearing many branches at its extremity, to 

 which in turn are attached the pedicles of the individual zooids. 

 Surface of bodies smooth. Nucleus band-like, curved. 



Length of zooids, 50 microns. 



Height of colony, 3,000 microns. (Figs. 194-196, PI. XXVII.) 



Figure 194 represents but a small fragment of a colony of this 

 species. In some instances these tree-like clusters are built up to 

 a height exceeding an eighth of an inch and contain several hun- 

 dreds of zooids. 



Figure 195 illustrates a single zooid of this species. 



From a physiological point of view Carchesium polypimini is of 

 no little interest. It is known what an essential part the nucleus 

 plays in the normal activities of the living cell and in this species 

 is illustrated the effect upon the nuclear elements of imperfect 

 nutrition. 



Miss M. Greenwood, in The Jonriial of Physiology, Vol. XX, pp. 

 427-454, sets forth the morphological elements enclosed by the 

 nuclear membrane of the nucleus of Carchesium polypinuni as 

 being the "nucleochyme" or fluid medium, the "microsomes" or 

 small granule-like bodies densely .scattered through the "nucleo- 

 chyme" and the "macrosomes" or larger masses, deeply staining 

 with certain dyes usually oval or rounded and which may be scat- 

 tered or arranged in a median line throughout the length of the 

 curved nucleus. Miss Greenwood found that after feeding Car- 

 chesium on an insoluble substance such as boiled white of egg the 

 usually deeply and uniformly staining macrosomes took on a 

 vacuolated appearance, some of them being represented by mere 

 shells with clear interiors. The conclusion drawn by Miss Green- 

 wood was that the normal activit)^ caused a drain on the organ- 

 ism which was not offset b)' sufficient repair, due to the lack of 

 nutrition, the result being shown in the more fluid character of 

 the macrosomes. 



Somewhat similar phenomena with respect to the nucleus of 

 Carchesium polypinum has come under my observation. I,ate in 

 December, 1904, individuals of this species were obtained from 

 the under side of stones in a pool near Iowa City. The}' appeared 

 as minute white masses, just visible to the unaided eye, and when 



