364 THE VOYAGE OF H.M.S. CHALLENGER. 



1866. DoHRX, Anton, born December 29, 1840 (Paul Mayer). 



Zur Naturgescbiclite der Caprellen. Mit. Taf. XIII. B. Zeitscbrift fiir wissen- 

 scbaftlicbe Zoologie. Bd. XVI. 1. Heft. 1866. pp. 245-251, 



Dolirn remarks, as Gosse had done before him, that Caprellse can upon occasion swim with 

 activity. In his account of the nervous system, he says that " the hrain mass consists of 

 two large, differently-formed swellings, of which the upper is considerably larger than the 

 lower. The former shows three distinct sections, a larger upper, a central giving off the 

 optic nerves, and a small anterior one. The upper mass is pierced by the two branches of 

 the aorta, the lower by the oesophagus ; behind this the broad oesophagean commissures 

 pass obliquely backwards, entering the first mass of the ventral chain, which likewise consists 

 of two coalescent ganglia. The hinder smaller ganglion belongs to the coalescent tirst 

 perfeon-segment and is considerably smaller than the anterior, properly subresophagean 

 ganglion." Mayer observes that the coalescence here spoken of is true of the genus Proto, 

 but in most genera and species of the CapreUidse, the ganglia in question come together 

 without actually coalescing. Dohrn cannot agree vnth Frey and Leuckart in the view that 

 the ganglion of the second periseon-segment is more powerfully developed than any other, 

 although he thinks that no doubt the importance of the ganglia depends on the extent of 

 the regions they have to supply. He studied the nerves in the young animal, but as a 

 matter of fact in some adult Caprellre the second pair of limbs are so greatly developed that 

 the statement by Frey and Leuckart is just in accord with the general principle which 

 Dohrn accepts. Dohrn found that the last perfeon-segment and the rudimentary pleon, at 

 any rate in the young animal, were without nerve-masses, but on the other hand he 

 discovered that the last ganglion, in the sixth periEon-segmerit, corresponded not merely to 

 two coalescent nerve-masses, but rather to five, some of which he naturally supposed were 

 derived from the pleon. Mayer, investigating young animals of Caprella and Protella, has 

 since seen " behind and between the two strong nerves that run from the seventh perron- 

 ganglion to the corresponding pair of legs, no less than seven ganglia, three pairs and an odd 

 one. The second and third pairs rapidly unite into a single mass, and do not appear to give 

 off any nerves. The last odd one shows traces of coalescence out of an original pair. It is 

 the largest of the pleon-ganglia, and no doubt, as Mayer says, corresponds to the single 

 ganglion which provides in the normal Amphipoda for the three segments preceding the 

 telson. 



Dohrn finds only two liver tubes in the CapreUidse, and therefore concludes that when Speuce 

 Bate speaks of the liver in the Amphipoda as consisting of four tubes, it is an error of 

 observation. The number, however, varies in different genera. 



In treating of the circulation, Dohrn attributes to the heart five pairs of fissures instead of three. 

 The first, he says, is in the cephalic segment, where the aorta parts from the dorsal vessel ; 

 the second, third and fourth lie in the middle of the corresponding segments. The fifth 

 lies in the middle of the fifth segment at the end of the dorsal vessel. The fourth is by 

 far the largest. 



In regard to the sexual organs, Dohrn supposes, but erroneously, that there are two pairs of 

 testes in Caprella, though in the other Amphipoda he is aware from concurrent testimony 

 that there is but one pair. 



