OBSERVATIONS ON THE GREGARINES OP HOLOTHURIANS. 283 



tinct septum could be discerned, dividing the animal in two. 

 This is probably an early stage in the encystation which we 

 shall discuss later. 



The best results were given by the two Gregarines which 

 were cut into sections, and which I shall denote as A and B 

 respectively. A was cut into sections of about lOju in thick- 

 ness, B into sections of about 5 — 7 fx. In A the relations of 

 the parts to one another were best shown, while B showed 

 better minute structure, the relations of the parts to one 

 another being often distorted. To begin with A : the entire 

 Gregarine ran through exactly forty sections. In the 14th 

 section from one end a nucleus makes its appearance, which 

 runs through five sections, disappearing after the 19th section. 

 Fig. 3 represents the 15th section, showing the blood-vessel 

 with the Gregarine in the interior x 128. Fig. 4 is the 

 interior part of the same section x 315. The 20th to the 30th 

 sections contain nothing special. At the 31st section another 

 nucleus makes its appearance, disappearing after the 35th 

 section. Figs. 5, 6, and 7 represent the 34th, 33rd, and 31st 

 sections respectively. The last five sections contain nothing 

 special. It is thus evident that this Gregarine contains two 

 large nuclei, each running through five sections 10 fi in 

 thickness. Similar results are given by B, which runs through 

 ninety-six sections. The first nucleus appears at the 10th 

 section, runs through eight sections, and disappears after the 

 17th. The second nucleus appears at the 78th section and 

 vanishes after the 85th. Fig. 8 represents the inner part of 

 the 80th section x 315, while 8 a represents the nucleus only, 

 from the same section, x 730. 



To proceed now to study the finer structure of these 

 animals. 



The body is limited by a distinct cuticle, appearing as a 

 sharp single contoured line, best seen in fig. 8, where the 

 Gregarine is not in contact on one side with the blood-vessel. 

 The protoplasm of the body is very opaque, and filled with 

 coarse granules of various sizes. No distinction could be 

 found between an ectosarc and eudosarc. 



