SCHIZOPOD 1«'E0M TASMANIA. 297 



Artlii'opoda, and will evidently repay close investigation. I tliink each cavity contains 

 a single row of these auditory hairs. 



I have already referred to the tactile and olfactory hairs of the antennas. 



Fragmentary and imperfect as this sketch of the anatomy is, it is sufficient to show 

 that in several respects the structure of Anaspldes is unique among Crustacea. The 

 abdominal caeca, the numerous isolated hepatic tubes, the simple tube-like heart, and the 

 curious structure of the auditory hairs are features peculiar to this Crustacean, differen- 

 tiating it not only from other members of the family Sehizopoda (from which Amspides 

 is also separated by its want of a carapace and external lamellate gills), but, I think, 

 from all other described Malacostraca. 



Affinities and Systematic Position. 



Anaspides is manifestly a schizopod shrimp, but its greatly generalized characters 

 as well as its remarkalile habitat point it out as a survival of a very old type. The most 

 conspicuous external features are the want of a carapace and the plate-like character of 

 the branchiae. Both are no doubt associated with its habitat among the clefts of rocky 

 pools, where its enemies were probably few and far between, and in which its body was 

 greatly protected, but the former feature especially seems to me indicative of the great 

 antiquity of the type. Until the full development has been worked out — and we know 

 absolutely nothing about it yet — it is impossible to arrive at any conclusions as to how 

 far the carapace is developed in the embryonic stages ; but, with this solitary exception, 

 1 know of no Crustacean belonging to the Thoracostraca in which there is absolutely 

 no trace of a carapace in the adult forms. 



In general appearance Anaspiides apjjroaches nearest among Sehizopoda to the family 

 Euphausiidse, with which it agrees in the following external features : — (1) the 7-jointed 

 pediform maxillipeds ; (2) the general uniform structure of the walking-legs ; and (3) 

 the well-developed natatory abdominal limbs, the first two pairs of which are modified 

 in the males as copulative organs. The points of dissimilarity are numerous enough, but 

 they are features in which it differs from all Schizopods, and not from the Euphausiidie 

 alone. Sars has shown* that in the Euphausiidge there are six principal stages of 

 development. After the young animal has passed through the Nauplius and Meta- 

 naiiplius stages, it enters on the Culijptopis stage, so-called by him after one of Dana's 

 spurious genera. In this stage, in which only the cephalic appendages are jiresent, 

 the carapace is attached to the anterior part of the body of the larva, and though it 

 pvojects backward to cover the portion which afterwards develops into the thoracic 

 segments, it is not anywhere joined to these segments, but only to the cepbalon. Even 

 at this early stage, however, it covers and comes to be attached to the somite which 

 bears the maxillipeds. Thus early in the development of a typical Schizopod has the 

 carapace come to be a prominent feature. It may here be pointed out that the 

 resemblance of the body of A// asp ides to that of a sessile-eyed Crustacean is not confined 

 to the want of a carapace and the occurrence of lamellate branchiae ; it is also suggested 



* Report on the Sehizopoda of the 'Challenger' Expedition, p. 150. 



