270 THEO. T. GROOM. 



Krohn, Willemoes-Suhm^ and Lang (Nos. 3, 7, and 9) have 

 proved that the prehensile antennules of the Cypris-stage in 

 the Thoracica arise from the first pair of Nauplius appendages 

 (antennules), and Delage (No. 10) has shown the same for 

 Sacculina. 



With reference to the fate of the remaining Nauplius 

 appendages, Metschnikoff,Willemoes-Suhm, and Lang (Nos. 3, 

 7, and 9) believed that both pairs were lost, and the first- 

 mentioned supposed that the mandibles and two pairs of 

 maxillae were all new structures formed inside a fourth pair of 

 appendages seen behind the third pair of Nauplius appendages. 



Claus, on the other hand, supposed (No. 8) from the analogy 

 of other Crustacea that the mandibles of the Cypris-stage arose 

 from the third pair of Nauplius appendages, the latter not 

 being lost like the second pair, but greatly reduced in size. 

 This observer did not, however, succeed in proving his point, 

 and I shall attempt in the following remarks to show that this 

 view is the correct one. 



The Cypris-stage, as is well known, possesses a well-defined 

 buccal mass. This, on account of its concealment within the 

 carapace, its small size, and delicate nature, as well as the 

 close packing of the component parts, is difl&cult to make out 

 satisfactorily. 



Darwin found in the Cypris-stage of Lepas australis 

 " all the masticatory organs of a Cirripede in an immature 

 condition.^' 



Pagenstecher (No. 4) describes the mouth-organs of the 

 Cypris-stage of Lepas pectin at a after fixation as consisting 

 of imperfect lobes and papillae without bristles or teeth. 



Willemoes-Suhm (No. 7) did not succeed in satisfactorily 

 separating the mouth-parts in Lepas fascicularis, but 

 describes the buccal mass as consisting of " three parts all 

 very rudimentary." 



Claus (No. 6) also describes three pairs of gnathites in an 

 undetermined Cypris-stage. These had the form of simple 

 outgrowths ; the mandible was largest and connected with the 

 labrum by a finger-shaped palp referable equally to the upper 



