EDRIOPHTHA LMIA . 



71 



FIG. 93. Limnoria Itg- 

 iiornm, gribble. 



thoa, Nerocila, and Anilocra} a peculiar type of hermaphroditism occurs. The youn-, 

 at a certain stage of development, have well-developed male organs, and also ovaries 

 but the oviduct has no external opening. Later in life the male organs are lost, while 

 the oviduct communicates with the exterior and the brood pouch 

 is developed. It has further been shown that these forms are in- 

 capable of self-impregnation. 



The little wood-boring Limnoria has a family (LIMNOEIDJE) all 

 to itself. Small as it is this little form docs a great amount of 



^j 



damage to wharves and shipping. Whenever wood is submerged 



beneath the salt-water these Limnoria lignorwn are apt to be 



found. The mandibles have sharp cutting-edges, and w v ith them 



the Limnoria eats its way into the wood, their immense numbers 



making them very destructive. Many plans have been proposed 



for preventing the ravages of the gribble, as it is commonly called, 



but none of them have proved very successful, and at the same 



time cheap. Possibly the best is the impregnation of the wood 



Avitli creasote, or "kyanizing." Limnoria occurs in the waters 



of Europe and America, and on our Pacific coast is said to do a great deal of damage, 



especially in San Francisco Bay. 



The IDOTEIDJE is the largest of the isopodan families, as well as the best known. 

 The body is usually long and slender, while several of the abdominal segments are 

 united into a large caudal plate. In this family the operculum of the respiratory cavity 

 acquires its most perfect condition. 



The genus Idotea is the most prominent in the family, 

 and our common I. irrorata has a very extended distribu- 

 tion in the northern hemisphere. It varies greatly in 

 color, closely resembling in this respect the rocks and 

 weeds among which it dwells. It is very abundant in 

 tidal pools along our northern Atlantic coast. Less com- 

 mon is Idotea phosphorea, which has the same habits, but 

 which is especially noticeable from its phosphorescent 

 powers. Our two species of Chiridotea (coeca and tuftsii) 

 are much broader than the typical forms of the family. 

 They live burrowing in the sand from near high-water 

 mark to about twenty-five fathoms. The name of the 

 first species is not very appropriate, for it is not blind. 



Passing by the MUNNOPSID^E, a small family of blind 

 marine Isopoda, we come to the ASELLID^E, the mem- 

 bers of which are found in both salt and fresh water. The 

 abdominal segments are united, the legs are fitted for 

 walking, while the eyes may be present or absent. Asettus is the typical genus, and its 

 members are common in the fresh waters of Europe and America. A blind form, 

 described under the generic name Ccecidotea, occurs in the waters of the caverns of 

 Kentucky and Indiana. 



The BOPYRIDJE embraces forms which are parasitic on other Crustacea. By 

 their parasitic habits the females have become greatly altered in shape, frequently 

 losing many of their appendages. They usually inhabit the branchial chamber of 

 decapod Crustacea, attaching themselves to the gills and sucking the juices of their 



FIG. 94. Idotea irrorata, en- 

 larged. 



