230 THE POPULAR SCIENCE MONTHLY 



also upon the affinity of the acid for certain protein substances of the 

 cell surface. 



Mr. Frank A. Potts, of Trinity Hall, Cambridge University, reports 

 that he found at the Murray Islands a small lobster-shaped crustacean 

 called Alpheus which lives among the arms of crinoids and usually re- 

 sembles the rich brown or mottled color of its host. Upon examining 

 some of these Alpheus, Mr. Potts noticed numerous small pink sac-like 

 bodies attached to their legs and these sacs contain the eggs and young 

 larva? of a barnacle-like animal which is evidently a parasite infesting 

 the Alpheus. In fact this degenerate barnacle grows within the tissues 

 of the Alpheus, and losing all semblance to a crustacean, changes into 

 a mass of root-shaped branches which at intervals send out sac-like 

 genital organs, these being the only special organs it possesses. When 

 the Alpheus moults, the sacs are cast off and each little larva is doubt- 

 less liberated to wander for a time as a free-swimming minute crusta- 

 cean and finally to find an Alplieus and to enter its body and change 

 into a root-like parasite, losing its eyes, legs, antennules, and all organs 

 of special sense to grow into a mere root-like form which sends out its 

 genital sacs upon the legs of its unfortunate host. The name of this 

 very degenerate creature is Thylacoplethus. 



Another curious animal which attracted the attention of Mr. Potts 

 was a crab called Hapalocarcirvus, the female of which settles down while 

 still very small and immature among the branches of the PocMopora 

 coral. Here the breathing of the crab produces a water current and this 

 causes the branches of the coral to thicken and finally to enclose the 

 crab in a capsule, leaving only a small aperture far too small to permit 

 of its escape, but large enough to admit the minute male of the species 

 who visits the chamber at the time the female moults. 



Professor David Hilt Tennent, of Bryn Mawr College, while at the 

 Tortugas Laboratory in Florida, discovered that the hybrid larva? of 

 certain echini can be caused to resemble either their father or their 

 mother in response to definite changes in the alkalinity of the sea- 

 water. The cytology of this matter has attracted much attention and 

 discussion, and Professor Tennent went with us to the Murray Islands 

 to continue studies of similar import and to study other hybrid crosses 

 between echinoderms. 



He caused an artificial cross to occur between a crinoid and an 

 echinus and carried the larva? farther than had previously been done. 



Some of Professor Tennent's best studies were carried out upon 

 Badu Island where members of the expedition enjoyed the privilege of 

 being the guests of the Eeverend F. W. Walker, the able managing di- 

 rector of the "Papuan Industries, Limited," which is devoted to de- 

 veloping arts and crafts among the natives thus to enable them to be- 

 come self-supporting in the broad civilized sense of the term, and to 



