60 CO. Whitman 



interests of a precocious and all-absorbiug- reproductive activity. In 

 failing to reach the ancestral condition. it failed also to reach a free and 

 independent existence. It lives, reproduces, and expires within the 

 mother. and its two kinds of ofifspring- are brought to complete develop- 

 ment under the protection . if not at the expense , of this same mother, 

 which thus sustains the relation» of a host not only to its own children, 

 but also to its more nnmerons grand-childreu. Kemarkable as such 

 relations certainly are , they preseut nothing fundamentally new to the 

 helminthologist. The Infusorigen — according to this \ iew — represents 

 an individuai which never gets beyond an embryonic condition , but 

 which nevertheless reproduces agamogenetically while enjoying the 

 protection of the parent , the latter holding to the Infusorigen relations 

 similar to those of a Distomatous sporocyst to its Cercarian ofPspring, 

 or to an intermediate generation of Radiae or sporocysts. That the pro- 

 tection of the parent should extend to the third generation is a phenom- 

 enon with which we bave been familiär since the investigations of 

 Von Siebold (46) and Gr. Wagener (49, p. 768) on Gyrodactylus. 

 According to both authorities the fourth generation arises before the 

 birth of the second ; and G. Wagenek states that even the fifth genera- 

 tion is already in progress of development by the time the second gener- 

 ation Tochter) is born. Van Beneden (1, p. 48) says that he has seen 

 a vermiform embryo within a vermiform embryo before the latter es- 

 capes from the parent. Carus mentions aninstance of a sporocyst (Amme) 

 containing Cercarian embryos within a larger sporocyst (25, p. 12). 

 The only difiference between such cases and the one bere considered is, 

 that in the former the successive generations are included the one within 

 the other , and set free in the order of their origin : in the latter the 

 second generation (the Infusorigen) is never set free, and cousequently 

 the third generation is thrown directly under the protection of the first. 

 The existence of the Infusorigen has been abbreviated to such an extent 

 that its maternity , so to speak, is practically obliterated , or replaced 

 by that of its own parent. It is hardly necessary to remark that we see 

 bere the possibility of a complete extinction of an intermediate genera- 

 tion. The nature and general bearings of such phenomena bave been 

 thoroughly and comprehensively discussed by Leuckart (44, p. 118 — 

 153, and 43, p. 81—119). 



The production of two kinds of germ- cells by the Infusorigen is 

 an interesting, though not an isolated fact. It is well known that many 

 rhabdocoelous Turhellaria produce '>summer« and »winter eggs«; and, 

 according to Metschnikoff (19, p. 299 — 300) and Korschelt (39, 



