NATURAL HISTORY OF AMERICAN LOBSTER. 309 



by a flattened membrane with double walls, representing the expanded capsule which 

 surrounds the egg. In most cases the hairs furnish support to but a small part of the 

 egg mass, the individual eggs being freely united with their neighbors. Thus in the 

 prawn Eucyphotes, according to Couti^re, the capsular cement gives off three or four 

 flattened bands, each of which is soldered at its apex to similar strands from other 

 eggs. The point of union is marked in each band by a lozenge-shaped or circular thick- 

 ening. This would indicate that the eggs are surrounded by a layer of the viscous 

 cement, and separated by sea water until they come together. Kach lozenge-shaped 

 thickening would then represent the original points of contact of egg with egg, the 

 strands being spun from the sheath by a mutual pulling strain, due to the weight of the 

 moving eggs. 



This condition is especially interesting since it seems to prove that such eggs must 

 have received their coat of cement before leaving the body. Unless it should appear, 

 however, that the marks of contact may be completely effaced by fusion of the united 

 strands, it offers no basis for a general conclusion regarding the origin of the cement 

 substance in other decapod Crustacea, like the lobster and crayfish. It is probable that 

 in this as in many other particulars there is no absolute uniformity. 



A much more anomalous method of fixation of the egg to the swimmeret is described 

 by Williamson {281) for the crab. Cancer pagurus, and in Brachyura generally. Accord- 

 ing to this observer, the eggs lie thiik upon the hairs of the inner branches of the swim- 

 merets, and are attached by independent and often intertwined stalks, but there is no 

 union of egg to egg, as in Synalpheus, Homarus, and other Macrura. The eggs are 

 attached to single hairs, which garnish the endopodites, and usually to hairs only. 

 There are said to be two membranes in either ovarian or attached egg, namely, a deUcate 

 vitelline membrane and a chitinous chorion. Between these a sUght perivitelline space 

 is formed upon contact with sea water. How does it happen that the eggs escape the 

 hairs of the exopodite, and how are they suspended to the silken hairs of the endopodite 

 without a single case of adhesion of egg to egg, and with little sticking of hair to hair? 



Williamson in brief offers this explanation: "The intimate relationship between 

 the egg and the hair is due to the hair acting as a skewer, upon which the eggs are impaled 

 and strung." Further, the hairs are supposed to penetrate the chorion and pass through 

 a perivitelline space without injury to the vitelline membrane. The chorion thus pierced 

 collapses, and a little albuminous perivitelline fluid is pressed out, which becomes adhe- 

 sive in sea water and serves to glue the chorion to the vitelline membrane and the egg 

 to the hair; later the glue and chorion is pulled out into the sheets or cords by which 

 the egg is anchored to the hair. 



The solution of the problem of fixation in the eggs of the blue crab appears to 

 carry us into deeper water than before. In order to make comparisons I have 

 examined the eggs and abdominal appendages of the blue crab, Callinectes 

 hasiatus. Callinectes lays upward of 4,500,000 eggs,<^ and the endopodites of the 

 swimmerets are buried out of sight by the mass. As in Carcinus these myriads of 



o Smith, S. I. : Report on the decapod Crustacea of the Albatross dredgings. Report of the Commissioner of Fish and Fish- 

 eries for 188s, p. 618-619. Washington, 1886. 



