490 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvm. 



On tho contrarv. thov can withstand a very great decrease in tem- 

 perature. Scott states that the a([uaria containing- LepeopJdJieJnis 

 prctoraUx were frozen several times witliout injury to the parasites. 

 Although this experiment has not been tried upon other species, 

 there is no reason to doubt that they could withstand as severe cold. 

 Itepeated trials have shown that the best way to keep these creatures 

 alive for any length of time, pai'ticularly during hot weather, is to 

 pack the a(|uarium or bottle in ice. Those species which are other- 

 wise prone to crawl up out of the water are much less likely to do so, 

 but secMU content to remain beneath the surface. Possibly this dis- 

 agreeal)le habit uiay b(> connected ordinarily with a rise in temperature 

 of the water in the a(iuariun], 



STTiMMARY. 



1. The females of the genera here discussed carry their eggs about 

 with them. This necessarily restricts their freedom of motion, l)ut 

 not to a greater extent than in free-swimming forms. 



'2. Added to the restriction, however, is a lack of incentive to free 

 swimming, since the parasite obtains its food upon its host and finds 

 there the best position for the aeration of its eggs. 



These two conditions combined constitute the tirst step toward 

 degeneration. 



3. These genera are really l)etter swinnners than the Argulidw, 

 owing to the increased surface of their swimming legs, particularly 

 the third pair. But they do not exercise this ability nearly as often 

 as the Argulida\ for the reasons just stated. 



4. In addition to their free swimming, the CuJigiis species also 

 exhibit the same scuttling motion as the Argulida^, and it is accom- 

 plished in a similar manner In- means of the sucking disks on the 

 frontal plates. 



5. In other genera the ^ucking disks are alisent, the scuttling 

 motion is impossible, and we tind still less of an inclination for free 

 swimming. Careful observations indicate that these genera remain 

 throughout life upon the same tish to which they attached themselves 

 in the chalimus stage. 



(>. As another' consequence of the loss of the scuttling motion they 

 remain for long periods in the same position upon their host, moving 

 oidy upon strong provocation. This fixity of position constitutes a 

 second step toward degeneration. 



7. For prehension we find the sucking disks in ('aJ!</us^ and stout 

 claws upon the second antennse and the second maxillipeds in all 

 genera. The edge of the carapace also, supplemented I)}' the broad 

 lamina connecting the third swimming legs, is flattened against the 

 supporting surface and functions as a large sucking disk. 



S. To prevent slipping backward under friction there are weak 

 spines upon the leases of the first swinuning legs, and a stout sternal 



