68 DR. LEIDY.— MISCELLANEA ZOOLOGICA. 



This singular enlozoon is a polygastrio animalcule. Its varied form and movements 

 are curious to observe ; at one moment globular, then oval, ovate, fusiform, sigmoid, 

 crescentic, &c., it appears as if it would outvie the kaleidoscope in its changes. 

 Sometimes it is collected in bunches adhering by the end of one of the cauda to 

 each other, and frequently it may be observed to contract upon either of the larger 

 cellules, causing them to project beyond the outline of the animal. The motions are 

 vibratile, rotary, with a lateral progression, or whirling in circles like the insec*: 

 Gyrinus. 



Cryptoicus, on account of its locality, might be mistaken for the spermatozoa of 

 the animal, but may be readily distinguished ; the spermatozoa of Helices generally 

 having either a uniform sigmoid or a spiral body, with an enormous proportionate 

 length of tail, and a slow, vibratile motion. 



In the collapsed state of the genitalia of Helices I could not detect the Cryptoicus. 



The subjoined sketch represents some of the varied forms of the animal highly 

 magnified. 



2. On the mechanism which closes the membranous 7vings of the genus Locusta.* 



The membranous wings or alae of the locusts while at rest are folded up, like a 

 closed fan, beneath the anterior pergamentaceous wings. These are opened or 

 expanded by the contraction of appropriate muscles (extensores alee) contained within 

 the thorax, the tendons of which are inserted into the ribs or longitudinal veins at 

 the root of the wings. When one of the wings is separated from the body of the 

 insect, and stretched open by the fingers, upon letting go, it will be found instantly 

 to close or resume the position of rest. 



The mechanism which produces this closure in the separated wing, as well as 

 when attached to the living animal, I find to be spiral ligamentous bands, wound, 

 like the thread of a screw, around the transverse or connecting veins, w^hich latter are 

 also flexible. By this arrangement, upon the contraction of the alary extensors, the 

 spring-like ligaments, or ligamenta spiralia as I will call them, are stretched in the 

 expansion of the wings, and upon the relaxation or cessation of the action of the 



*Proc. Acad. Nat. Sci., Vol. iii. p. 104, 



