Male of Apus cancriformis. 121 



modified for holding the female, such as occur in its ally 

 Branchipus ; but none exist. 



It is usually stated, on Kozubowski's authority, that the 

 male is about one third shorter than the female, with a dis- 

 tinctly narrower abdomen and flatter carapace. These state- 

 ments can scarcely be said to be true in the present instance. 

 The male did not differ noticeably in size from the rest of the 

 specimens, some of which were slightly larger, others smaller. 

 1 measured one female, taken at random, and found the trunk 

 (excluding the head, that is) to be 36 millim. long; the 

 trunk of the male is 33 millim.; the diameter of the female 

 abdomen, close to the last appendage, is 5 millim., that of 

 the male 4 millim. 



Sir John Lubbock has recorded (1863) that the males of 

 another species, Lepidurus productus, are larger than the 

 female. We cannot, then, make any general statement as to 

 proportionate size of the two sexes. 



On referring to Mr. Bernard's little book, i The Apodidse,' 

 I was rather surprised to find that no mention of the anatomy 

 of the male Apus occurs in the body of the book ; but in the 

 appendix he quotes his letter to ' Nature,' vol. xliii. p. 843, 

 in which he gave a brief history of the observations on the 

 male. The name of Kozubowski does not appear in his list 

 of references, nor that of von Siebold. Seeing that Bernard's 

 book is the only recent English account of the anatomy of 

 Apus, it is regrettable that space was not found for a reference 

 to the sexual difference. But no doubt a description of the 

 mere anatomy of the animal was not so much his aim as a 

 comparison of Apus with an Annelid. Moreover, he wished 

 to emphasize the hermaphrodite nature of Apus. 



Now it is more than four years since Mr. Bernard an- 

 nounced, in a brief note published in the 'Jena. Zeitsch.,' the 

 discovery of the existence of testes, or, at any rate, of " sperm- 

 producing centres," in the female Lepidurus; but beyond 

 stating that he has observed the same state of things in some 

 other species, and has seen spermatozoa in the lower part of 

 the duct, he has not materially added to this bare statement 

 either in his book or elsewhere. I think it is not an exag- 

 geration to say that zoologists have been impatiently waiting 

 for a detailed and illustrated account of this phenomenon. 

 Apus has for so many years been regarded as partheno- 

 genetic, that naturalists hesitate to accept the bald statement 

 that it is " hermaphrodite and self-fertilizing." 



On p. 309 of his book Mr. Bernard writes : — " The sperm- 

 producing centres were found scattered here and there among 

 the rich branches of the segmental diverticula of the genital 



