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or free extremity — but this is not the case. In the other larger (nearly full-grown) specimen 

 I have investigated, I did not observe this papilla or, better perhaps, excrescence. In two of 

 them I observed the two closely approximate, flattened points mentioned by Darwin as being 

 present between the bases of the last cirrus. These are considered by Darwin as the caudal 

 appendages in an extremely rudimentary condition ; close outside these rudimentary points on a 

 slight swelling is the anus, according to Darwin. I need hardly point out that the excrescence 

 as figured by me would not be called a slight swelling by Darwin. I may add that I could 

 distinguish a small porus behind this excrescence, between it and the free projecting part of the 

 oblique fold — whether this porus really represents the anus I have not been able to make out. 



It is not the place here to enter into more details with regard to the anatomy of this little 

 male. With the material at my disposal it would hardly have been possible to penetrate much 

 farther into the mysteries of its structure than Darwin did by dissection and Gruvel (1. c.) by 

 apjDlying the more modern method of cutting sections. There are several points of great interest 

 connected with these males — I think they will offer a very fruitful subject of research to the 

 zoologist who studies their anatomy as well as their biology at the place where he finds them 

 on the coral-reefs. 



An important point yet to be made out is their metamorphosis. They pass no doubt 

 through a Cypris-stage ; but the youngest stage observed by Gruvel in all essential points — ■ 

 but for its immatureness — resembles the grow'n-up male. Darwin observed the larvae of 

 /. qiiadrivalvis in this stage and distinctly saw "all the essential points of structure in the 

 larvae of other Cirripedes at this stage" but he did not observe the metamorphosis itself. 



Another essential point would be to determine whether or not these little males feed 

 independently. Darwin supposes that the male Ibla seizes its prey with its mouth through the 

 movement of its long flexible body and I cannot understand how it would do otherwise ! But 

 Gruvel seems to admit that the male lives parasitically on the female : derives its nutriment 

 from the much bieafer female. He came to that conclusion from the fact that the wall of the 

 stomach is not furnished with calyciform cells, that he could not find a trace of digestive glands 

 and that the stomach of the specimens he investigated did not contain food. But taking into 

 consideration the perfectly well-developed mouth parts, the long oesojahagus, the rather large 

 .stomach I think it difficult to share Gruvel's opinion in this regard. How could they take 

 nutriment, if not with their mouth or digest it if not with their alimentary canal? The body and 

 all its appendages are covered with chitin; the only direct attachment to the wall of the female 

 is originally by means of the prehensile antennae, the cement glands situated in the undermost 

 part of the peduncle afterwards secreting quite a cushion or ball of cement which imbeds these 

 antennae. I need hardly say that from that side no food can enter the body of the male. 



I found the .structure of the cement-glands, -ducts etc., as also that of the male genital 

 organs, the more or less compact globular balls composing the testicles and the double pear- 

 shaped vesiculae seminales in accordance with Darwin's and Gruvel's descriptions — these 

 parts may be considered as well known. Perhaps the nervous system is not so well known as 

 yet. Gruvel describes two ganglionic masses, the one lying dorsally from the alimentary canal 

 and representing the cerebral (supra-oesophageal) ganglion; the other lying ventrally from the 



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