TENTACULATA LOBATA 



419 



::Ct. 



gastric 



loin 



multicornis. These tentacles have no sheaths, and do not bear 

 pinnae. They are probably not, homologous with those of other 

 Ctenophora. 



The characters that separate the families of Lobata are chiefly 

 those of varying size, shape, and position of the peristomial lobes 

 and auricles. In the Lesueuriidae the peristomial lobes are rudi- 

 mentary ; in the other families they are moderately or very large. 

 In the Bolinidae the auricles are short, but in most of the other 

 families they are long and ribbon-like. In Euckaris they can 

 be spirally twisted in repose. 



The modifications of the external form seen in the Lobata 

 are accompanied by some modifications of the internal structure 

 Among these, perhaps the 

 most interesting is a 

 communication between 

 the transverse longi- 

 tudinal and the para- 

 canals, and the 

 convoluted tubes 

 given off to the peri- 

 stomial lobes by the 

 sagittal longitudinal 

 canals. Very little is 

 known about the life- 

 history and development 

 of most of the Lobata, 

 but Chun has shown 

 that in Bucharis and 

 Bolina there is a Cydip- 

 piform larval stage which 

 produces ripe ova and spermatozoa. This is followed by a period 

 of sterility, but when the adult characters are developed they 

 become again sexually mature. To this series of sexual pheno- 

 mena the name " Dissogony " is given. 



The order contains only fifteen genera, but they are usually 

 arranged in the following eight families : 



1. Lesueuriidae. Lesueuria. 



2. Bolinidae. Bolina, Bolinopsis. 



3. Deiopeidae. Deiopea. 



4. Eurhamphaeidae. Eurhainphaea. 



F.L. 



Fig. 181 



Ocyroe crystallina. Ab, aboral sense- 

 organ ; au, auricle ; Can, diverticulum from the 

 paragastric canal passing into peristomial lobe ; 

 Ct, costae ; M, mouth ; Par, paragastric canal 

 passing outwards to join one of the transverse 

 subcostal canals ; P.L, peristomial lobe ; w, wart- 

 like tubercles on the lobe. (After Mayer.) 



