CHONDRACAXTHUS GIBBOSUS. 



seems to be connected with a subjacent gan^lionic mass. 

 The body is suiViciently transparent to allow the pulsaii-.ns 

 of a heart to be seen, but none can be 1 I. 'I'll.- ' 



is ;i larire oval hilobed mass (), lyin^r like a saddle upon the 

 anterior part of the intestine. From this body a thick vas 

 deforms runs hack upon each side of the intestine, and <ii 

 latfs in the penultimate and antepenultimate somi 

 thick walled pyriform sac u sort of vesicula seminal is. The 

 embryo leaves the egg as a Nau/>l!>i*, like that of Cyclops. 



There are many genera of these parasites, some of u hi h, 

 such as the almost completely vermiform JLerncefe, deviate 

 even more widely than Ckondracanthut iVom the ordinary 

 form of Crustacea, while others, such as Eryaxilus and Nbto- 

 i, dilVer but little from the free Copepoda. 



In ('<///'r//fx, the labium and metastoma are elongated and 

 united into a tube in which the sharp styliform mandibles are 

 inclosed ; and from the prevalence of this suetorian form of 

 mouth in some of the best known species of parasitic Cope- 

 poda, they are frequently termed "suctorial" crustaceans. 

 Suctorial disks for attachment are developed from the coa- 

 lesced posterior pair of thoracic members in Achtheres / and, 

 in this genus, the head, as a distinct pan, becomes almost 

 entirely obsolete. 



.1/7//////.V, the parasite so common on the Stickleback, is 

 worthy of notice as one of the most curious modifications of 

 the epizoic type. 1 It is extremely flattened, a;ul is composed 

 of an anterior ceplialo-thoracir disk, behind which li-> a 

 short and broad, notched abdomen. A median styliform 

 weapon lies in a sheath in front of the mouth, and the small 

 mandibles and maxilla 1 are inclosed in a short tube formed 

 by the labrum and the metastoma. Six pairs of appendages 

 lie behind the month, the anterior brin_r metamorphosed int.. 

 suckers, the next pair into strong limbs with a toothed 

 ond joint, and the four others constituting biramons swim- 

 ming-feet, There are two pairs of antennary organs, and two 

 compound eyes. According to Levdiir, the m pro- 



vided with cups on their penultimate swimmiji iiid, 



during copulation, these are tilled with the seminal fluid, 

 which is thus transferred to the vulva of the female, and 

 thence to the spermathoca. The eir^> an- laid, and not 

 ried about in ovisai-s. The larva U provided with two pairs 



1 CUuB( u UeberdieEntwickelun^OrmliatJonundr - 'nng 



der ArgnHden," 1876 fa* proved the cl<>8< aftinil ''opt- 



poda, but proposes to regard it as the type of a special group, the Branch! ura. 



