202 DISCOVERY REPORTS 



fin, but, at a mantle length of 25 mm. or more, it is quite possible that the larval fin was in the last 



stages of resorption. The specimen is tentatively assigned to stage 4. 



Specimen No. 97 is also interesting. Anterior fin buds cannot be seen on account of the poor 

 condition of the specimen, yet, at a mantle length of 10-5 mm., it is most improbable that they were 

 not originally present. The eye diameter indicates that the true mantle length may even have been 

 somewhat greater, perhaps as much as 13 mm. The specimen may be assigned to stage 2 with some 

 confidence and it may further be noted that, at the observed mantle length of 10-5 mm., the anterior 

 fin rudiment was probably a triangular bud about 0-3 mm. in length. 



Sex and stage. The preceding discussion permits a clear statement regarding developmental stages ; 

 sex is determined by the presence or absence of a penis or penis rudiment which is visible even in 

 very young male larvae. 



The collection contains one half-grown adult, specimen No. 99, a female. Two specimens, Nos. 103 

 and 104, are in the final stage of metamorphosis with only minute posterior fin rudiments. Both 

 these specimens are males as also are three more which have been assigned to the last larval stage, 

 viz. specimens No. 96, 98 and 102. As noted above, however, specimen No. 96 may really have already 

 lost its larval fin. The remaining specimens consist of a four-finned larva (stage 3), which is specimen 

 No. 101, a female, and two stage 2 larvae in which the anterior fin is a mere rudiment. One of the 

 latter (specimen No. 97) cannot be sexed on account of poor preservation, nor can the anterior fin 

 bud be seen although, as noted above, it must certainly have been present. Specimen No. 100 is 

 rather well preserved although the mantle is everted, an anterior fin bud is present and the sex is 

 almost certainly female as there is no trace of a penis rudiment. 



Primary cirri. Previous investigations have brought to light the interesting possibility that there 

 may be small racial differences between the Vampyroteuthis populations of the Atlantic and Indo- 

 Pacific Oceans. Atlantic specimens appear to have one more pair of primary cirri, i.e. cirri that 

 precede the first sucker, on the arms. The difference is not an absolute, all or nothing character, but 

 far more Atlantic specimens have the larger number, and far more Indo-Pacific specimens the 

 smaller. 



Table 4. Number of primary cirri 



The data for the Discovery specimens are tabulated in Table 4 and the results are summarized in 

 Tables 5 and 6. It will be seen that the Discovery specimens contribute nothing towards the hypo- 

 thesis of racial difference, in fact, for the first time, an Atlantic specimen (No. 104) is found to have 

 a minimum number of four pairs of primary cirri. Nevertheless the overall data are still heavily 

 weighted in favour of the racial hypothesis. The majority of Atlantic specimens have 8 or more pairs 

 of primary cirri on the first or second arms (31 specimens out of 46); the majority of Indo-Pacific 



