APPENDIX TO MEMOIR OF TELTIER. 175 



numerous observations on tlie common and tlio scutolliform arcella?. Tbo 

 motlier-arcella begins b}' extending, under the form of a large disk, a portion 

 of her membrane. This portion of membrane is attached to the horny shell by 

 prolongations at regular intervals. It is at fii'st perfectly smooth, of great trans- 

 parence, and contains no other substance ; when its formation is finished, a por- 

 tion of the glutinous matter of the mother flows upon it. In one instance Pel- 

 tier saw this glutinous substance flow too abundantly on the new membrane 

 and leave but about a sixth of it for the mother ; the current now stopped, then 

 retrograded, and an inverse current was established for the benefit of the primi- 

 tive arcella. An instant afterwards, Avhen the original current had been re-es- 

 tablished and again conveyed the vivifying matter on the young disk, it once 

 more surpassed the bounds and left the arcella too much impoverished. It was 

 not until after five or six oscillations of this sort, the amplitude of the flow 

 diminishing each time, that a due distribution was effected and the intercommu- 

 nication ceased. The vascular filament which united the two arcella? gradually 

 became thinner, then entirely separated, and two minutes afterwards the two 

 distinct animalcitles withdrew one from the other, both thrusting out their arms 

 and performing their customary digitations. This mode of generation is cer- 

 tainly very remarkable ; we here see the half of a living creature flowing out- 

 wardly and forming with this excreted moiety an animal in all respects similar 

 to the moiety remaining. 



Peltier observed, in 1830, another example of generation by an efflux of sub- 

 stance still more curious than the former, for here the efflux was not sponta- 

 neous. He had placed between two glasses, under the microscope, a drop of 

 water in which there was a very large specimen of ]\Iuller's vesicular leucophra; 

 in slightly compressing the two glasses, the external membrane was broken and 

 perhaps a hundred of the globules which fill the animal were extruded. Many 

 of these were scattered about in being projected by the pressure, but others 

 clung together in a space of small extent. The former remained apart, and 

 nothing was remarked in them but the tremulous motion of light bodies. The 

 globules of tlie agglomerated portion, on the contrary, gradually drew closer 

 together, grouped themselves, and finally, at the end of an hour, formed a 

 sphere whose contour, of a brilliancy inclined to nacreous, indicated the forma- 

 tion of a membrane. At the end of two hours there was perceivable in the cir- 

 cumference the reflection of the liquid in motion, and shortly afterwards the 

 oscillations of very fine cilia. The leucophra was now complete and presently 

 revolved upon itself, then spontaneously changed its place and traversed the 

 drop of water. Thus this little animal was produced externally l)y the agglome- 

 ration of the substance which had been made to issue mechanically from the 

 mother. 



Transformations of zoospcrms. — Peltier had followed with much attention the 

 successive transformations of zoosperms, especially those of the frog.* He 

 show^ed first that the spermatic liquor expressed from the testicles contains, in 

 winter, only simple spherical globules. As adolescence approaches, and the 

 season of copulation, these globules become covered with black points and small 

 projections, which latter speedily elongate, forming each a cone, the point of 

 which appears filamentous and soon undergoes much enlargement ; at the same 

 time the filaments which terminate these cones grow more and more distinct and 

 present the appearance of a tuft of hairs. The cones thus terminated by fila- 

 ments consist of small masses of zoosperms, attached by the head to the black 

 points of the central glol>ule, and free in their caudal extremity. 



As long as these globules swim in their natural liquor, no movement is per- 

 ceived ; but if there be mixed with it blood from the neighboring veins and 

 arteries, the point of the tufted cone partiall}^ opens and some of the filaments 

 which terminate it commence oscillating with their terminal parts. If blood 



* Journal VInstitut, 1838, t. vi, p. 132. Idem., 1840, t. viii, p. 392. 



