ox LMJISTISPfRA VKXEUIS XOV. SPEC. 525 



The explanation of these appearances i^, I Ijelieve, quite 

 simple. As will be shown in the next section of this paper 

 (vide infra), the method of multiplication is by transverse 

 fission. The daughter-individuals which arise from the 

 transverse division of a long individual are therefore short — 

 being only half the length of the original organism. Before 

 they undergo a subsequent division they must grow in length, 

 and must therefore form new chambers. I believe that these 

 new chambers are formed at various points in the body, and 

 arise by the gradual thickening of a partition and its subse- 

 quent hollowing out. Thickened partitions therefore corre- 

 spond to the points where new chambers are beginning to be 

 formed — more darkly stained chambers are newly formed 

 chambers. Successive stages in the formation of cluimbei-s 

 in this way are shown in fig. 8 (where a thickened septum 

 is seen at h), fig. 9 (which shows the hollowing of the septa at 

 two points), and fig. 6 — where a darkly staining- (newly 

 formed) chamber is seen at a. 



(2) Division. 



Although I have not been able to observe every stage in 

 division in the living organism, I have encountered a number 

 of dividing forms in my stained preparations which leave no 

 room for doubt as to the essential features of the process. 

 Division is transverse, and is effected in the manner described 

 by Gi'oss in the case of C. pectinis. I have never seen 

 any indications of a longitudinal division, and all the observa- 

 tions which I have made speak strongly against the view that 

 such a method of multiplication occurs in these organisms. 



The long individuals which are about to divide into two 

 transversely are in the form of spirals consisting of five or 

 six complete turns. Before dividing, they bend themselves 

 double — the two halves becoming intertwisted (see fig. 4). ' 

 This phenomenon has been described in C. pectinis by 

 Gross, who calls it " incurvation."'' The transverse fission of 

 the organism begins when it is in this condition. It occurs 



