238 



CTENOPIIOR.^. 



Part II. 



■which is llattenod at the base of attachment.^ In this condition it is easy to 

 observe that each cell is covered exteriorly by a single layer of exceedingly minnte 

 granular bodies (PI. IP Fiffs. 7, 0, and 12 /). As the tentacle contract.s, the lasso- 

 cells become mutually compressed ; at first but slightly [Fiffs. 16 and ■ 17), but 

 finally so as to be sharjily polygonal {Fi(/. 13 a). The granular coating is so dense 

 that the coiled thread within is not so conspicuous as in the lasso-cells of the 

 Discophonv. Even with a magnifying power of five hundred diameters, it is very 

 difficult to detect the thread whilst the cell remains attached to the tentacle, 

 and then it is seen foreshortened ; for a profile A'iew is out of the C|uestion, except 

 when the tentacle is stretched to the utmost, and then, owing to its activity, only 

 a mere glimpse can lie obtained. The only convenient metlK>d of observing them 

 is by cutting oft' one of the fringes, when with unusual readiness the lasso-cells 

 drop awa}^ from their attachment. If now they are j^laced upon a glass slide 

 they nuiy be rolled about in every direction, and thus exposed in any desired 

 position. Xo satisfactory elucidation of the nature of these cells can lie obtained 

 by using objectives of ordinary definition.*, for the granular coating is confounded 

 with every thing el.<e;- but, in order to plunge into the midst of the contents 



' It is not possible to see these cells in this 

 condition nnlcss the objective of the microscope is 

 plunged without ceremony into the water of the 

 deep jar in which these animals must be kept. 

 By gradually cooling the water until it becomes 

 icy cold, a small quantity will serve to keep Me- 

 dusa; in the full vigor of life, and then they may be 

 observed without mutilation. Unless the bi-ass-work 

 be varnished, the chemical reaction of the sea- 

 water invariably disturbs the animal, and causes it 

 to contract very closely. "With a little care, a power 

 of from three hundred and fifty to five hundred 

 diameters may be used. 



- Gegenbaur, who was the first to publi-h any 

 thing about these cells (Wiegmann's Archiv, ilarch, 

 185G, p. 1711, Taf. VIII. Fi'g. 12 e {'). gives a very 

 meagre account of them, and shows that he does 

 not know their typical difference from the lasso- 

 cells of the discoid Medusa> and all Polypi. Ilis 

 brief notice of the lasso-cells of what he considers 

 a new species of Cydippe — but which is probably 

 a new genus — reads thus: "Both the cirrhi and 

 the margin of the appendage are covered by round 

 nettling cells, 0,005'" in diameter (by mistake for 



0,005", no doubt), which inclose a smooth, spiral 

 thread. If the thread extrudes, it shows the pe- 

 culiarity of not straightening out at once, as do 

 all other lasso-threads observed by me, but remains 

 for some time in a long drawn out spiral. The 

 end remaining, during protrusion, within the vesicle, 

 stands in connection with a number of round gran- 

 ules, which are grouped in a blackbcrrv-like form." 

 Later in the same year. Dr. T. Strethell TVright 

 (Edinburgh Xew Phil. Mag. October, 185G) also 

 published a brief notice of these cells, which repeats 

 the errors of Gegenbaur, and adds nothing new 

 whatever. The animal which he examined was 

 a genuine Pleurobrachia, if it was the same as the 

 one he refers to in the July number of the Journal 

 of the same year. He says : " These cells were 

 spherical, and opaque from the presence of mole- 

 cular matter in their interior, "When ruptured by 

 pressure, they were found to contain a simple short 

 thread, more or less closely coiled in a spiral form. 

 The application of distilled water burst the cell 

 walls and uncoiled the threads." From the above 

 it is evident, that neither Gegenbaur nor Dr. 

 Wriirht had studied the lasso-thread whilst coiled 



