48 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxi. 



Bay of Biscay, 800-1,200 meters (A. Milne-Edwards and Caullery); 

 west coast of Ireland, 382-600 fathoms (Holt and Tattersall); Azores, 

 1,000 meters (Hansen); near Maldive Islands, 130 fathoms (Alcock and 

 Anderson). Typical form, as G. willemoesi: Banda Sea, 1,425 fathoms 

 (Sars); Gulf of Panama, 1,270 fathoms (Faxon); off Acapulco, 493-664 

 fathoms (Faxon); Tres Marias Islands, 680 fathoms (Faxon); Hawaiian 

 Islands, Molokai and Hawaii, 552-809 fathoms (Ortmann). 



G. zoea sarsi: Bay of Bengal, 840 fathoms (Wood-Mason); Hawaiian 

 Islands, vicinity of Kauai and Moclu Manu, 293-800 fathoms (Ortmann). 



THE LAKVAL FORM OF GNATHOPHAUSIA ZOÈA. 



As previously mentioned, among the material is a large female of 

 this species, representing Sars's form G. willemoesi, which has the mar- 

 supial pouch fully developed and filled with larvae. Since larval stages 

 of this genus have never been described, indeed, since nothing is 

 known about the development, with the exception that on account of 

 the presence of a marsupial pouch and in analogy to Lap hog aster it is 

 presumed that the development of the young form probably reaches a 

 very advanced stage before it leaves the mother, it is advisable to give 

 here a more detailed account of these young specimens. 



The number of the young is 21, a remarkably small number, but 

 agreeing well with w T hat we know about the number of the progeny of 

 deep-sea animals. The}^ are all uniformly developed and represent a 

 very advanced stage, in fact, they are no longer embryos, but have 

 left the egg completely. Probably they were about ready to leave the 

 pouch of the mother, as all parts of the body had attained, in a general 

 way, the condition found in the free swimming form. 



Within the pouch the young Gnathophausiae are so arranged that 

 they lie firmly packed together, the head of each directed toward the 

 posterior end and the sternum of the mother, and the tail toward the 

 anterior end of the mother, each overlapping in part the individual in 

 front of it. That is to say, the heads are directed toward the bases, 

 the tails toward the tips of the marsupial lamellae. The dorsal face of 

 the larvae is concave, the ventral face convex, corresponding to the 

 curvature of the lamellae, since the back is turned toward the sternum 

 of the mother, the ventral side toward the enveloping lamellae. 



In each of the young ones (see Plate II, fig. 2a) the body is distinctly 

 divided into an anterior (thoracic) and posterior part, which forms a 

 distinctly and completely segmented abdomen. The carapace is rep- 

 resented by a bag-like excrescence, which is provided with distinct 

 and long rostral and póstero- dorsal spines. It is filled with the rem- 

 nant of the yolk. Its keels are very indistinct, but there is a small 

 point posteriorly on each side, possibly representing the postero-infe- 

 rior corners of the carapace. The dorsal spine is long and closely 



