12 Mr. Lubbock 



The species which I have named Diaptomus duh'ius is one of 

 those intermediate forms whose phice is very difficult to deter- 

 mine. It makes one hnk of a series which connects Puiite/la with 

 Calanus. There appear to he two snch series, one of whicli con- 

 tains Hemkalanus cnlnninus, Da., H. tenuicurnis, Da., and the 

 other the species which Dana has formed into the group Cala- 

 ncpia, which he considers to be a siil)genus of Pontella. Diapto- 

 mus dubius belongs to the latter group, hut is, if I may use the 

 expression, on the Calanoid side of it. The absence of inferior 

 eyes, and the structure of the maxillipeds, are sufficient to prove 

 that it cannot be considered i\ Porilella, while the structure of the 

 inferior antennse exclude it from Hemicahinus. I have been 

 obliged, therefore, to place it in Westwood's genus D'inptunius, 

 although it resembles more nearly the species in Dana's sub- 

 genus Calanopia. I am very averse to multiplying genera, but 

 *' Calanopia " appears to me to have far more claims to that rank 

 than " RhincalanusJ" Many facts seem to favour the opinion that 

 there is no such thing as a well marked genus in Nature, but that 

 every intermediate form either does exist or may have existed in 

 Nature; and that to say that any group is well marked, is equi- 

 valent to saying that there are many forms with which we are 

 unacquainted. We may expect therefore that such species as D. 

 dubius will become more and more frequent as our knowledge 

 increases. 



I have requested Dr. Baird to give me his opinion of the proper 

 place of this species. He considers that it belongs to his genus 

 Temora. It may be necessary to remind Naturalists that the 

 genus Calanus was founded by Leai-h on the Cyclops Finmarchi- 

 cus, which was both imperfectly known and incorrectly described. 

 Dr. Baird rectified the descriptions and, considering that the 

 falsity of Leach's characters vitiated the genus, described it as 

 Temora Finmarcliica. Even he, however, was only acquainted 

 with one sex, so that we had thus two genera founded on one 

 species, and that one very iinperfectly known. The characters 

 given by Dr. Baird as those of Temora (Calanus) Finmarchicus, 

 are those of a large numl)er of Enlomostraca, and Dana con- 

 sidered that by the rules of the British Association Leach's name 

 ought to be used. Although I regret to be obliged to difler from 

 my much respected friend Dr. Baird, I feel myself obliged to come 

 to the same conclusion as Professor Dana. Now, however. Dr. Baird 

 considers that we have become acquainted in this species [Diapto- 

 mus dubius) with both sexes of Temora, and that the characters 

 must accordingly be altered. Lilgeborg in his excellent work "On 



