394 DESCRIPTION or {Volygasttica. 



The folio-wing obscn-ations are from more recent investigations of 

 Ehrenberg : — 



In tbe small pools left by the ebb of the tide near Ciixhaven, he 

 remarked numerous little bodies, apparently similar to KavicuU, 

 ' Surirella elcgans, and S. striatula, but which, from their compara- 

 tively very great size and structure of lorica, were easily distinguish- 

 able from them upon closer examination. One of these ribbed oval 

 glass-like creatures, which belonged to the genus Naricida, was, 

 besides its size, remarkable for its great mobility, and Dr. E. was 

 enabled to investigate its system of locomotion much more satis- 

 factorily than he had hitherto done in any member of the genus. 

 This organ he states was very different, both in form and size, to what 

 he had before noticed. Instead of a snail-like expanding foot, long 

 delicate threads projected where the ribs or ti'ansverse markings of 

 the shell joined the ribless lateral portion of the lorica, and which 

 the creature voluntarily di-ew in or extended. An animalcule 1-1 8th 

 of a line long had twenty-four for every two plates, or ninety-six in 

 the total ; and anteriorly, at its bread frontal portion, four were 

 visible. The openings for the pm-poses of nutrition appeared to be 

 at the extremity. Whether these organs were supernumerary, and 

 existed along with cirrhi, &c., and the flat snail-like foot, which the 

 rest of the Nmiculm possess, could not be determined. Longitudinal 

 clefts at the broad side of the shell were not present, but as many as 

 ninety-six lateral openings for the exit of the cirrhi were perfectly 

 distinct. It is probable this creature may form the type of a special 

 group of the BacilJaria. Of one thing Dr. E. is convinced, that the 

 Kavicula in general are very differently constituted indi\-iduany ; 

 thus, in some cases, the six round openings in the little sheU are dis- 

 tinctly visible, whilst in others, clefts, which in some cases gape, 

 and are unprovided with circular openings, are all that can be 

 made out. 



The fleshy, undi-\dded, sole-like foot, Ijang close upon the lorica, 

 described by Ehrenberg in some of the large forms of Naviculce, has 

 not been observed by any other microscopist. Kiitzing says he has 

 failed to discover this locomotive process, though he has searched 

 most narrowly after it. Neither, again, have Ehrenberg's views, re- 

 epecting the presence of locomotive ciha, capable of being protruded 



