ISOMETRA VIVIPARA. 39 



ular masses staining dark blue, while the nuclear masses have a beautiful 

 violet color; also, the shape of these nuclear masses is very peculiar, recall- 

 ing certain magnificent beard fashions (plate xvii, figures 3 and 7). The 

 epithelium of the vcstibulum is distinctly ciliated; the cuticula is seen in 

 sections to be perforated, while a regular layer of fine grains is seen just 

 below the cuticula (plate xvii, figure 5). 



The suctorial disk is large and deep (plate xvi, figure 2; plate xvii, figure 8; 

 plate XVIII, figures 3 and 8). The cells contain a finely granular substance 

 (plate XVIII, figure 9), which stains red in hcmatoxylin-cosin, thus appearing 

 remarkably different from the glandular cells of the vcstibulum, which stain 

 dark blue, as stated above. A slimy mass fills the cavity of the disk, probably 

 representing cilia, destroyed by the preservation. The cuticular structure 

 observed in the vcstibulum (plate xvii, figure 5) could not be distinguished 

 here, even in the same series of sections which showed this structure distinctly 

 in the vcstibulum. There is no indication of an apical tuft of cilia. The 

 pigmentation has already begun to develop in the skin of the larva before 

 leaving the egg-membrane, viz, some fine, dark spots which give the larva 

 a faint grayish tint. 



The nervous system is fairly well developed (plate xviii, figure 3), but not 

 BO distinct in the sections as to allow a detailed description. Neither are 

 its histological relations to the epithelium of the suctorial disk distinct 

 enough to show whether the development of the nervous system takes 

 place in the same way as has been described for Antedon by Seeliger (op. 

 cit., p. 238). On the other hand, there is no reason to doubt that there is 

 cornplete conformity in the development of the larval nervous system of 



the Crinoids. 



The vestibulary invagination is remarkably narrow (plate xvi, figure 2), 

 though there is, of course, some variation in this regard, evidently due to 

 contraction on preservation. (See plate xvii, figures 1 to 4, compared with 

 figures 6, 7, and 9 to 12 on the same plate.) K. A. Andersson {op. cit., p. 6) 

 states that "die Vestibulareinstulpung zeigt dem gewohnlichen Verhaltnis 

 gegenuber darin eine Verschicdenhcit, dass sie am Vorderende am tiefsten ist 

 und dass sich das Verschliessen von da aus voUzieht." It is true that the 

 invagination is deeper at the anterior end, but the same holds good for the 

 other Crinoids thus far known in this regard, Antedon as well as Tropiotnetra 

 and Compsovietra; so there is herein no difference from the condition which 

 may now with more justification be termed the "usual" mode than it could 

 be at the time K. A. Andersson wrote his paper, when Antedon was the only 

 type of which the development had been studied. Regarding the other, 

 much more important, departure from the "usual" type pointed out by 

 K. A. Andersson, that the closure of the vcstibulum starts from the anterior 

 end, I can not see how he has come to this conclusion, for there is not the 

 slightest doubt that it starts from the posterior end as in the two other 



