352 ON THE STRUCTURE OF NOCTILUCA MILIARIS 



To this doctrine M. de Ouatrefages also attaches the weight of 

 his authority in his valuable essay ' Observations sur les Nociiluques^ 

 published in the Annales des Sciences Nat. for 1850. M. de 

 Quatrefages does not admit the existence of any true mouth or 

 intestinal canal, and considers that the so-called stomachs are nothing 

 but 'vacuoles' similar to those observed in the Rhizopoda and 

 Infusoria. 



In a short memoir published in Wiegmann's Archiv. for 1852,. 

 however, that excellent and most accurate observer, M. Krohn, carried 

 the subject a stage further, and showed that the organization of 

 Noctiluca is more complex than has been supposed. Krohn carefully 

 describes and figures the mouth of Noctiluca and the long vibratile 

 cilium, which he was the first to observe, proceeding from it. Krohn 

 draws particular attention to the oval body first described by 

 Verhaeghe, which he considers to be the homologue of the ' nucleus ' of 

 the infusoria ; and describes the ejection of faecal matters. Arranging 

 the Noctiluca among the Protozoa, Krohn points out some interesting 

 structural analogies with Actinophrys and Pai-amcEciuni. 



I will now proceed to detail the results of my own observations. 



Noctiluca ntiliaris (Plate V. [XXVII.] figs. 1,2) may be best described 

 as a gelatinous transparent body, about i-6oth ^ of an inch in diameter, 

 and having very nearly the form of a peach ; that is to say, one surface 

 is a little excavated and a groove or depression runs from one side of 

 the excavation half way to the other pole {echanci'ure, Quatrefages, 

 Frauenbnsencihnliche Einbucht, Krohn). Where the stalk of the- 

 peach might be, a filiform tentacle, equal in length to about the 

 diameter of the body, depends from it, and exhibits slow wavy 

 motions when the creature is in full activity. I have even seen a. 

 Noctiluca appear to push repeatedly against obstacles, with this tentacle.. 



The body is composed of a structureless and somewhat dense 

 external membrane, which is continued on to the tentacle. Beneath 

 this is a layer of granules or rather a gelatinous membrane, through 

 whose substance minute granules are scattered without any very 

 definite arrangement. From hence arises a network of very delicate- 

 fibrils, whose meshes are not more than i -3000th of an inch 

 in diameter (fig. 6), and these gradually pass internally, — the 

 reticulation becoming more and more open — into coarser fibres,, 

 which take a convergent direction towards the stomach and nucleus. 

 All these fibres and fibrils are covered with minute granules, which 

 are usually larger towards the centre. 



'The extremes of size are given by Krohn as 1-7 — i millimetre = 1-170 — 1-25 inch, 

 about. 



