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flesh ; the spiral corkscrew manner of entenng accounting for the 

 pain, and for its short duration. Out of tlie water, the knob 

 adheres to the finger ; and when drawn back a little, the bundle 

 of fine hair-like filaments in the reflection of the light becomes 

 visible to the naked eye. 



On the return of the U. S. Exploring Expedition, a distin- 

 guished anatomist examined the drawings of these thread-vesicles, 

 and pronounced them " spermatozoa." Dr. P. had never seen 

 unequivocal spermatozoa ; and could not say, whether they are 

 animals or organs. The above-described thread-vesicles are 

 unquestionably organs ; and ai'e identical with the "lasso-cells" 

 observed by Agassiz in other zoophytes. In the Physalia, the 

 thread-vesicles were observed sometimes to become detached 

 spontaneously, floating off" with tlie filament closely coiled in the 

 interior, ready to shoot forth. The analogy with pollen deserves 

 perhaps further inquiry ; especially as zoophytes, in their struc- 

 ture, station, and the surrounding external circumstances, have 

 many points in common with plants. 



Prof. Agassiz said that he had made minute examinations of 

 the lasso cells upon living coral. To illustrate the difficulty 

 attendant upon such a study, he cited the fact that as eminent a 

 naturalist, even, as Rudolph Wagner, at first described them as 

 spermatozoa, and that they have even been considered as clusters 

 of parasitic Vorticellfe. Prof. Agassiz found that these bodies were 

 globular or ovate cells, containing a coil, and that the two forms 

 existed in every part of the body, although one form was gen- 

 erally more abundant than the other. The lasso is really a tube, 

 which, in its extension, is inverted, and the continuity of the cell 

 and tube can be readily determined. The mechanism by which 

 the inversion is effected is a series of stiff bristles, which are 

 within the tube when it is contracted, and which serve as a 

 spring to invert and distend the thread, the bristles then coming 

 upon the external surface. The tubular thread does not always 

 uniformly taper, but sometimes suddenly contracts in size. As 

 to their relations as sexual organs, they appear to be equally 

 numerous in males and females. Prof. A. wished to be under- 

 stood that what he brought forward as new was the direct evi- 

 dence that the thread is hollow, and that it is everted in the 

 process of throwing out. 



