NATURAL HISTORY OF AMERICAN IvOBSTER. 313 



whether devoid of processes of every kind, or provided only with three stiff rays as in the 

 lobster, under ordinary conditions of observation these cells are absolutely immobile. 

 Still every thoughtful observer who has pronounced the decapod sperm to be immovable 

 must eventually recant, and like Galileo declare, " E pur si muove." How then could such 

 sedentary bodies seek, find, bore through the tough shell and fertilize the egg ? Brandes, 

 Labb6, and Koltzoff have offered or worked out fertile suggestions, which afford a satis- 

 factory solution to the general problem, subject to a course of verification and extension 

 in different species of crustaceans. 



That the "immobile" sperm cells really did move, has been maintained for thirty 

 years or more by Owsjannikow, Hermann, and Cano. Thus apropos to this subject 

 Grobben (122) remarks: "The stiffness of the rays does not prove that these cells are 

 completely immobile. Moreover, the observation of Owsjannikow that the rays some- 

 times draw themselves in, and certain structures which I have examined, enables me to 

 conclude definitely that these rays are living protoplasm and that they represent amce- 

 boid processes, remaining almost in a state of rest." (Compare the observation of Cano 

 quoted below.) 



In 1890 Hermann {138) had described movements of the processes of sperm cells, 

 and in 1893 that excellent observer, Cano {46), spoke of seeing "certain of the sperm 

 cells, especially the rayed ones, in amoeboid movements in the sperm receptacle of the 

 crab Maia." 



In 1896 a remarkable statement regarding independent movement in the sperm 

 cells of the lobster was made by Bumpus (42), to the effect that he had "seen the sper- 

 matozoa in active movement, swimming across the field of the microscope with the 

 same nervous contractions that are characteristic of the Hydromedusae." 



In 1897 Brandes (js) asked how it was possible for the decapod sperm to enter an 

 egg where no micropyle could be found, and especially in sperm cells like those of Astacus, 

 which have no pointed head, but which are spherical and of considerable size. "I 

 suppose that the sperms at the moment of contact with an unfertilized egg undergo a 

 change, which consists in this, that a more or less pointed part of the anterior end of 

 the sperm, the so-called clapper, the "tigelle" of French writers, is evaginated and so 

 the membrane of the egg which at the moment of egg laying is perhaps somewhat 

 yielding, is perforated." This ingenious suggestion, which was elaborated at greater 

 length, has proved very fruitful, for it was confirmed by Labbe in 1903, and especially 

 by Koltzoff {172) in 1906, who has worked out the development and structure of the 

 sperm cell in a number of Brachyura, such as Portunus, Maia, Pagurus, and Eupagurus, 

 and of Macrura in Homarus, Galatkea, and Scyllarus. 



According to these later observers, the sperm cell is a very comphcated and delicate 

 machine, beside which a clock or watch seems like a crude affair, especially when we 

 consider the vast difference in size. This cell may be compared to a self-propelling 

 torpedo, designed to move in a certain direction, and to explode the moment the cap 

 or head strikes the hull of a vessel, or any opposing object. 



