REPORT ON THE AMPHIPODA. 549 



1884. Blanc, Henri. 



Contribution h, I'histoire naturelle des Asellotes heteropodes. Observations 

 faites sur la Tanais Oerstedii, Kroyer. Avec les Planches X, XI et XII. Recueil 

 zoologique Suisse (Dr Hermann Fol). Tome premier. No. 2. Sorti de presse le 28 

 fevrier 1884. Geneve-Bale. pp. 189-258. 



Dr. Blanc agrees with Lilljeborg in referring the two species Tanais rhijncMtes and Tanais 

 halticus of Fr. Miiller, as respectively male and female forms, to the older Tanais oerstedii, 

 Kr0yer. The description which he proceeds to give bears on the disputed question, whether 

 the Tanaida3 should be reckoned among the Amphipoda. In Tanais oerstedii, he says, the 

 heart extends along the back from the last thoracic ring to the hinder rim of the cephalo- 

 thorax. In this species, as in Tanais savignii, it possesses only two pairs of ostioles 

 (venous orifices), whereas for Tanais duhitis ? Miiller reckons three pairs, and Delage 

 only one pair for Tanais vitfatus. The ostioles are situated in the second and third free 

 segments of the pereeon. Besides these, the heart has five arteries, the cephalic artery 

 and two abdominal arteries described by Delage, and in addition two thoracic arteries as 

 large as the cephalic, arising, opposite one another, from the ventral part of the heart, below 

 the two ostioles in the second free thoracic segment, and running a ventral course to the 

 first thoracic feet. 



In conclusion Professor Blanc says, " the characters which bring the Tanaidse near to the 

 Isopods are more numerous [than those which connect them with the Amphipoda and other 

 groups]. The general form of the body is that of the Isopods. The body is flattened, the 

 sixth and seventh segments of the pleon are, as in the Isopods, soldered together and form 

 a caudal lamella, Avhile in the Amphipods these two segments are distinct. The number of 

 ganglia in the ventral chain of Tanais Oerstedii is the same as in certain Isopods, as 

 Cymothoa, Ligidium ; in the Amphipods the number ig less considerable, the abdominal 

 ganglia being reduced to four or three. The five pairs of abdominal feet, as in Anceus, 

 are all alike ; since they play a part in the act of respiration, they are not the biramous 

 feet of Amphipods. In the latter group, the urinary secretion is situated in the antennary 

 glands and the glandular appendages of the rectum [of the midgut, according to P. Mayer] ; 

 these glands are wanting in the Tanaidae as in the Isopods, in which the urinary secretion is 

 situated in the fatty bodj'. Lastly, the absence of the seventh pair of feet in the embryos 

 of the Tanaidaj and the Isopoda is an important character which distinguishes these 

 Crustacea from the Amphipoda, of which the embryos are born with the same number of 

 appendages as they have when adult." 



One point in this argument loses some of its force from the fact that the sixth and seventh 

 abdominal segments are occasionally soldered among the Amphipoda, in the tribe Hyperina. 

 The absence of lateral arteries was considered by Delage to show a nearer connection of the 

 Tanaidas with the Amphipoda (Gammarina) than with the Isopoda, but this point of 

 resemblance can no longer be relied on since Professor Blanc's discovery of the lateral 

 arteries in Tanais oerstedii, nor yet on the other hand can the presence of these arteries be 

 relied on as any special link between the Tanaids and Isopoda, since Glaus finds lateral 

 arteries in many genera of the Amphipoda (Hyperina). 



Gerstaecker, 1886, is by no means convinced by Professor Blanc's arguments, and, as will 

 be seen, retains his conviction that the Tanaid® ought to be classed among the 

 Amphipoda. 



