124 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 



may be noticed in the same pool duriug the progress of the seasons. 

 In these cases, according to our nomenclature, the modified form is a 

 post imago, and if young born from the ordinary female enter this 

 state and produce young in turn which never reach that state, we 

 have a case of what was termed "heterogenesis" in the old general 

 sense; i. e., two cycles of development occur in the same species. Now, 

 as these cycles are dependent on environment, the process may be 

 termed ptedogony if the term is taken in the sense indicated. What 

 to do with such cases is puzzling to taxonomy. It is obvious that they 

 are quite different from the sporadic appearance of sexually functional 

 larvse, for here we have a stage which does not necessarily belong in 

 the history of the species, and is, as it were, superinduced. The objec- 

 tion raised by Schmeil against making varieties of them — i. e., that 

 you cannot fix an arbitrary size limit — would militate against almost 

 all geographical varieties equally. In fact, however, the changes fol- 

 lowing the last moult are usually evident enough to produce no trouble. 

 In the case of Cyclops signatus we are confronted by a question of fact. 

 This is undoubtedly the most conspicuous instance, if an instance at 

 all, of the change referred to. If the actual rearing of G. signatus var. 

 coronatus should prove that G. signatus var. tenuicornis does not belong 

 in its cycle then the two forms must be separated and this particular 

 instance of psedogony disappears. We think it possible, however, to 

 prove the contrary. Most remarkable of the many curious statements 

 made by Schmeil on this i^oint is the following: ^'Herrick even in his 

 later work is not in position to demonstrate among the known species 

 a single sexually mature larva. He is not in the position to bring a 

 proof of a single one of his assertions. Also none of the other investi- 

 gators has observed this, according to Herrick, common phenomenon," 

 Having overlooked my earlier paper he is surprised at the failure to 

 again revert to it. But, after his own admissions, how he can deny 

 the evidence of sexually mature larvie is unintelligible. 



FAMILY HARPACTICID^. 



Numerically the largest of the families of the Gopepoda, this group 

 contains predominatingly marine and mostly minute animals, fre- 

 quently of strange and grotesque form. A few of the marine forms, in- 

 habiting the Gulf of Mexico, are figured in the report of the Minnesota 

 Academy of Sciences for 1881. Of the over thirty genera of the family 

 less than a half dozen are not exclusively marine, and of these most are 

 brackish -water residents. The genus Bradya contains blind Gopepodm 

 living in slime. 



The name was proposed by Dana, but was dropped in the final 

 report. Again revived by Glaus, it is now in use by the best authors. 



