;66 



MICROSCOPIC FORMS OF ANIMAL LIFE 



the light ; and its tail-like appendagCj whose length .-iliout equals 

 its own diameter, and which serves as an instrument of locomotion, 

 may be discerned with a hand-magnifier. The form of Xoctiluca, is 

 nearly that of a sphere, so compressed that while 011 one aspect (fig. 

 f>87, A) its outline when projected on a plane is nearly circular, it 

 is irregularly oval in the aspect (B) at right angles to this. Along 

 one side of this body is a meridional groove, resembling that of a 

 peach ; and this leads at one end into a deep depression of the sur- 

 face a. termed the atrium, from the shallower commencement of 

 which the tentacle, d, 1 originates ; whilst it deepens down at the base 

 of the tentacle to the mouth, e. Along the opposite meridian then- 

 extends a slightly elevated ridge, c. which commences with the 

 appearance of a bifurcation at the end of the atrium farthest from 



B 



: -::.:, "\*&^\ >%^C% ':,- 



i$:;:^illi 5 ^?- : ^:: 



/A A \ .,: 







FIG. 587. Noctilt/c/i miliaris as seen at A on the aboral side, and at 

 B on a plane at right angles to it : a, entrance to atrium ; I/, atrium ; 

 a, superficial ridge; d, tentacle; e, mouth leading to oesophagus, 

 within which are seen the flagellum springing from its base, and the 

 tooth-like process projecting into it from above ;/, broad process from 

 the central protoplasmic mass proceeding to superficial ridge ; g, 

 duplicature of wall; h, nucleus. (Magnified about Hit diameters.) 



the tentacle : this is of firmer consistence than the rest of the body, 

 and has somewhat the appearance of a rod imbedded in its walls. 

 The mouth opens into a short (esophagus, which leads directly down 

 to the great central protoplasmic mass ; on the side of this canal, 

 farthest from the tentacle, is a firm ridge that forms a tooth-like 

 projection into its cavity ; whilst from its Hoor there arises a long 



The organ here termed ' tentacle ' is commonly designated ffiifjel/iun ; while 

 what is here termed the flagellum is spoken of by most of those who have recognised 

 it as a i-iliinii. The Author agrees with .M. Robin in considering the former organ, 

 which has a remarkable resemblance to a single fibrilla of striated muscle, as 

 one peculiar to Xotlil/icit . and the latter as the true homologue of the flagellum of 

 the ordinary Flagellata. It is curious that several observers have been unable to dis- 

 co 1 er the so- called ci 1 nun . which \vas lirst noticed by Krohn. Professor Huxley sought 

 for itin at least fifty individuals without success ; and out of the great number which 

 lie afterwards examined lie did not 'jet a. dear \ lew of it in more than half a dozen. 



