222 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



(1) The chain has held together not only during the more or less 

 violent disturbances involved in making a plankton haul with a silk net 

 from a vessel at sea, but also during the microscopical examination in 

 the course of which it has been rotated several times in freeing it from 

 entangling organisms and in securing dorsal and ventral views. It has 

 also survived the changes of fluid incident to the staining process and a 

 final transfer from a 4 per cent solution of formalin in sea water through 

 alcohol grades to glycerine, made by passing the fluids through beneath 

 the cover glass. In the course of these changes it has been subjected 

 to some bending and strains, but has not parted except as shown 

 (plate 3) in the figure of the cell contents, where the junction of cells 

 II 8 and III 3 is slightly disconnected. 



(2) The connections between the apical horns of II 3 , III 3 , IV 8 , and 

 the attachment area at the distal ends of the girdles of I 3 , II 3 , and I1I 8 , 

 respectively, are both normal and typical. I have studied with especial 

 care under the oil immersion lens the details of the most important con- 

 nection, namely, that between the apical horn of IV 8 (Ceratium tripos 

 representative) and the cell (III 3 = C. californiense) to which it is at- 

 tached anteriorly. This is in all respects perfectly typical, even the 

 protoplasmic bridge appearing to be still intact. 



(3) The apices of all the horns, save the ancestral one, which is on 

 the anterior skeletal moiety of I 3 , exhibit the flaring, slightly lobed mar- 

 gin about the apical pore, described by Entz (1905), which is character- 

 istic of this part of recently formed anterior horns. These are the con- 

 ditions to be expected in a normal chain of four individuals. 



(4) Contrasts in the hyalinity and porulation of the anterior and pos- 

 terior moieties of the skeletal wall of the several individuals are indicative 

 of recent normal chain formation. These differences are due to the fact 

 that the skeletal wall grows darker with age and its pores are more easily 

 seen. This is plainly noticeable in the case of III 3 and IV 3 , upon whose 

 recent separation by division the whole point of this communication 

 rests. The anterior skeletal moiety of IV S in the original specimen is 

 very plainly of a more delicate texture than the posterior one, barring 

 only the right antapical region which has apparently recently exuviated 

 or is undergoing resolution. The posterior moiety of III 8 is likewise of 

 a lighter texture than the anterior one of that individual, though the 

 difference between them was less striking than in the case of the two 

 regions of the skeleton of IV 8 . These contrasts are just such as would 

 appear if III 3 and IV 8 had recently originated by the division of the 

 posterior member of a chain of two schizonts. Differences of similar im- 



