studies on mariiio OstivifOfis 357 



excluded. The last-mentioned possibility seem, however, rather improbable because an utteinj)! 

 at parthenogenisis that was carried out by G. W. MOller on a female of a nearly related species. 

 Ph. (Ph.) interpunda, had a negative result. (Cf. G. W. Mulleh, 1894, p. 175.) 



The males seem to die fairly soon after copulation. — This is supported by the two follow- 

 ing circumstances: 1) Among the larvae the males and the females are found in about equal 

 numbers, as has been pointed out above. Among the sexually mature specimens, on the other 

 hand, the females predominate very strongly in number over the males, the latter being in most 

 cases very rare. (I speak here of the bottom samples.) It does not seem probable that this 

 scarcity is due to the fact that the mature males more frequently avoid being captured in the 

 dredge owing to their greater rapidity. 2) The most important reason in favour of this 

 assumption is, however, that when the males reach sexual maturity, their jaws are very much 

 reduced, they become quite imfit for dissecting food — ,,welche beim Eintritt der Geschlechts- 

 reife unfahig werden, Nahrung aufzunehmen", G. W. MtJLLER, 1894, p. 188. G. W. MiJLLER 

 investigated, 1894, the stomachs of sexually mature males of this genus and found them 

 empty. The same was also true of the stomachs of the male specimens of Ph. (Ph.) (jlubom 

 investigated by me. 



Another important result shown by the above table is that no clear periodicity can be 

 observed in the appearance of this species: 



1) Mature females with emptied brood chambers, the oldest specimens, were found 

 in February, March, May, June, July, August and September. 



2) Mature females with their brood chamber filled with eggs were found in all months, 

 from January to September. 



3) Mature females with broken swimming bristles on the second antenna and the 

 eggs not yet pressed out into the brood chamber from February to September. 



4) Mature females with long, unbroken swimming bristles on the second antenna in 

 January, March, April, May, June and August. 



5) Mature males in January, March, April, August and September. 



6) Larvae in the first and second stages were found in all months from January tt) 

 September except in February. 



It is to be noted here that the only February sample that I had access to was very poor; 

 it contained only the six specimens given in the table. This deficiency in individuals is certainly 

 to be explained by the incompleteness of the collection. The sparse occurrence of young larvae 

 in most of the samples investigated is certainly due to the same cause. 



Unfortunately there were no samples from the last three months of the year. It seems, 

 however, quite certain that all the categories mentioned are to be found also during these months. 



The fact that mature males, which — as has been pointed out above — certainly live only 

 a short time after the last larval moult, and females with long natatory bristles on the second 

 antennae are to be found during all parts of the year definitely indicates that this species has no 

 limited period for copidation; on the contrary, this fact makes it very probable that copulation 

 takes place at all times of the year. Another consequence of this fact is, of course, that this 

 species is to be found in the plankton during the whole year. 



