390 CALKIXS. 



The nucleus oi Anixba protciis can be regarded as similar to 

 that of CJiilomonas plus a nuclear membrane. There is no evi- 

 dence of other intra-nuclear bodies such as linin, nucleoli, etc., 

 nothing is present but chromatin and the central body. I'he 

 tough nuclear membrane is possibly due to the peculiarly rough 

 treatment which the nucleus undergoes in its cyclosis with the 

 other endoplasmic substances. 



Ceratiuni and Peridiiihim. Biitschli ('85) found a very curious 

 structure in the dinoflagellate nucleus. Viewed from one side it 

 appears to be of the regular reticulate type with local thickenings 

 on the linin network ; but, looked at from another side, the nu- 

 cleus seems to be composed of rows of chromatin connected by 

 delicate fibrils, the whole having a more or less honey-comb 

 structure. Lauterborn ('95) confirmed Biitschli's description but 

 added that the nucleus invariably contains one or two nucleoli, 

 and that in division a peculiar rod-like body of *' unknown signifi- 

 cance " stretches across the division axis. Lauterborn is inclined 

 to believe this structure homologous with the intra-nuclear body 

 of Euglena. I have examined a number of Dinoflagellata from 

 Puget Sound and Alaska including Peridiniuin divergens^ Dino- 

 physis, Ceratiiiui tripos, Ceratiuni fusus, etc. and in all of them I 

 have found the familiar intra-nuclear central body, differing 

 however from the more frequent type in being sometimes single, 

 sometimes double or multiple. (Figs. 21 Peridiniuin divergens, 

 and 20 Ceratium fnsus.) The peculiar rod-like or even lamel- 

 late structure of the chromatin is perhaps due to the fusion of 

 chromatin granules, thus forming a permanent structure com- 

 parable to a spirem. 



Noctiluca niiliaris (PL XXXV, Figs. 22-26). Of very 

 different structure is the nucleus of Noctiluca miliaris^ a form 

 possibly allied to the Dinoflagellata. The chromatin here is 

 massed in from eight to eleven large reservoirs (Fig. 22), 

 while the rest of the nucleus is filled with a granular sub- 

 stance of quite a different chemical composition. The whole 

 is enclosed in a firm membrane. This nucleus would be diffi- 

 cult to understand were it not for the changes which the chro- 

 matin undergoes previous to division. The large reservoirs 



