36 RESEARCHES ON FUNGI 



protoplasmic continuity between the peg and the hook becomes 

 established (E). 



In a completely formed clamp-connexion the part contributed 

 by the peg can still be distinguished from that contributed by the 

 hook, for where these parts became united there is usually a slight 

 groove (Figs. 18, E, and 19, B. C, and D). 



In one clamp-connexion of Coprinus lagopus the time which 

 elapsed between the first formation of the hook as a tiny rudiment 

 and complete fusion between the hook and the peg was 23 minutes. 

 If the time at which the hook was first observed beginning its growth 

 be taken as the zero of the time-scale, then the times at which the 

 successive stages shown in Fig. 18 were attained were as follows : 

 A, 3 minutes ; B, 15 minutes ; C, 21 minutes ; D, 22 minutes ; 

 and E, 23 minutes. The first septum to be formed— that across the 

 main hypha — was observed as a definite structure at the end of 

 14 minutes. Since, as we know from the cytological investigations 

 of Mile Bensaude, the conjugate division of the nuclei does not begin 

 until the hook has become well advanced in growth, and since nuclear 

 division must be over by the time the first septum has been formed, 

 we may conclude that conjugate nuclear division in C. lagopus under 

 laboratory conditions takes less than 14 minutes and is probably 

 accomplished in about 12 minutes. 



Before the hook and peg of a clamp-connexion have fused with 

 one another, a nucleus is imprisoned in the clamp-cell (Fig. 21, 

 p. 45), and protoplasmic continuity between the ultimate and penul- 

 timate cells of the main hypha is limited to the bridge of protoplasm 

 stretching through the pore of the septum in the main hypha 

 (Fig. 18, D). As soon as fusion has taken place, the imprisoned 

 nucleus escapes from the hook into the penultimate cell of the hypha 

 (Fig. 21) ; while, at the same time, the protoplasmic continuity 

 between the ultimate and penultimate cells becomes strengthened, 

 for protoplasm now extends without a break around the hook and 

 through the pore of the septum situated at the base of the hook 

 (c/. D and E in Fig. 18). 



Nine successive stages in the formation of a clamp-connexion of 

 Coprinus sterquilinus are shown semi-diagrammatically in Fig. 19, A. 

 In a hanging drop of cleared dung-agar at room temperatures, all 



