6 PROCEEDlNGki OF THE NATIONAL MUSEUM. vol.53. 



In 1815-16 Oken published a Lehrbuch Naturgescliichte, in 

 which he placed the Lernaeans as the third family in the order of 

 ■■ Erdleche oder Geschlechtsleche," and in this family were included 

 all the parasitic copepods then known (p. 181). Later, in the same 

 hook (p. 357). he revised his classification, which contained many 

 errors and called the group "Armwurmer," dividing it into two 

 tribes, the Lernaeans containing four genera, Axine, C'lavella, Pen- 

 nella, and Lernaea. and the Argulids, containing also four genera, 

 Anops\ Dichelestiurn, Caligus, and Argulus. Thus was shown for 

 the firr^t time the relations between the Lernaeans and the other 

 copepod parasites. In 1817 Cuvier, in his Eegne Animal, adopted 

 the view taken by Bosc, placing the Lernaeans among the intestinal 

 worms, while he located the other parasitic copepods among the 

 Crustacea. 



Soon afteiw ards Surriray made the important discovery that the 

 long filaments suspended from the body of these animals contained 

 eggs and that the young when hatched bore no resemblance to the 

 adults, but were very similar to the young of Cyclops — that is, they 

 were crustaceans and not worms. 



Blainville, in his Memoire sur les Lernees (1822), admitted the 

 truth of Siu-riray's statement and fully established the Lernaeans 

 among the Crustacea, where they have remained ever since. 



ECOLOGY. 



Sexual dimorphism. — The females of the Lernaeidae are fixed 

 parasites, and consequently there is a complete loss of the power of 

 locomotion, although the swimming legs are usually retained, and 

 there is great diversity in the means of prehension. Since the male 

 does not finally become a fixed parasite, but remains upon his first 

 host or swims about freely until his death, there is not the sexual 

 dimorphism which was seen in the Lernaeopodidae. Indeed, it can 

 not be said that there is any real dimorphism at all, because so long 

 as the two .'Jexes remain together and during the period of sexual 

 union they are of the same size, and it is only after the female has 

 become a fixed parasite for the second time and the male has perished, 

 that the former increases enormously and becomes misshapen. 



The body of the female is always a little longer than that of the 

 male, and just before as well as for some time after fertilization the 

 genital segment increases greatly in length, but remains of the same 

 width, thus giving the female larva an exceptionally elongated form. 

 A considerable portion of this increase takes place during the sec- 

 ond free-swimming period, so that by the close of this period there 

 is a marked difference in the length of the fused genital segment 

 and abdomen between the female and such males as still survive; 

 but in other respects the two sexes are alike. 



