FRESH-WATER MUSSELS. 85 



BREEDING. 



The internal phenomena connected with reproduction are presented in connection 

 with the discussion of Hfe history (Part 2, p. i38fif). We have to do here only with the very 

 few external manifestations which have been observed as related to the breeding 

 activities. 



The eggs are fertilized by sperm emitted into the water by males and taken in 

 with the inhalent current of the female. In a few species the females, when about to 

 spawn, are marked by a striking development of lurid colors and elongate flaps on the 

 margin of the mantle about the inhalent orifice. In addition to the bright colors there 

 are peculiar spasmodic movements of this part of the mantle. This peculiarity has been 

 observed in a good many pocketbooks, Lampsilis venlricosa, in a few fat mucktts, 

 LampsUis luteola, in some L. radiata, L. orbiculata, L. higginsii, and L. ovata (grandma), 

 and in nearly all of the L. midtiradiala which have come under observation. (See Clark 

 and Wilson, 1912, p. 54; Wilson and Clark, 1912, pp. 13, 14; and Evermann and 

 Clark, 1918, p. 284.) Ortmann (1911, p. 319) has described such flaps in Lampsilis 

 ventricosa and L. tmdtiradiaia. He observes that when the gravid females are undis- 

 turbed the marsupia are pushed outward, so that they project out through the inhalent 

 opening and even a little beyond the shell, as previously figured by Lea. The waving 

 flaps lie alongside the marsupia, and he attributes to them a function in promoting a 

 current of water over the marsupia. It seems more probable that these conspicuous 

 flaps, which sometimes suggest the appearance of small fish, may serve as a lure to fish, 

 bringing them into desirable proximity to spawners when the glochidia are ready for 

 extrusion, thus rendering the fish liable to infection and so increasing the chance of 

 survival of the glochidia. The following is quoted from Wilson and Clark (1912, pp. 

 13, 14): 



The mussels were thickly scattered everywhere, with especially dense beds along the shore. The 

 small fish were again noticed playing about in the immediate vicinity of the spawning mussels. 



L. ventricosus has a habit of moving its bright-yellow siphon fringes, which are much enlarged during 

 spaivning, back and forth in the water. This undulatorj- motion seems to attract the small darters 

 and minnows, particularly Nolropis blennius, which could be seen darting in toward the fringes 

 repeatedly. It also probably assists in furnishing fresh water for the respiration of tlie yoimg mussels. 



At intervals during the undulations small numbers of glochidia are discharged from the brood 

 chambers of the mussel and carried out of the e.KCurrent aperture. These glochidia are of the hookless 

 type, and must be taken into the mouth of the fish that is to carry them during their parasitic period. 

 We can thus understand the advantage of attracting these fish and keeping them in the immediate 

 vicinitj' during the discharge of the glochidia. 



WINTER HABITS. 



Very little is known of the habits of fresh-water mussels in winter. Observations 

 of rate of growth indicate that growth practically ceases during the very cold months. 

 (See Isely, 1914; and also p. 132.) Microscopic studies of sections of shell indicate that 

 there are numerous slight interruptions and resumptions of growth, corresponding to 

 each period of winter, and these are no doubt related to the fluctuations of temperature 

 in fall and spring. 



According to clammers, mussels cease to "bite" with the approach of cold weather. 

 The obser\'ations of Evermann and Clark on the movement of certain mussels from the 

 very shallow waters near the shore of Lake Maxinkuckee in late fall have been pre\aously 



