102 CALIFORNIA ACADEMY OF SCIENCES. 



PLATE XXXV. 



PONTODEILUS MICHAELSENI. 



40. Cross-section tbrongli somite xvii of a mature specimen showing the developnieut of the clitellar cells ou the 



dorsal aiul lateral sides of the clitellum. i'. cl. ventral termini of the clitellar cells. d. v. dorsal vessel. 

 ,9. !. sacculated intestine. neph. nephridium. yl. pr. glandular part of prostate. pr. m. muscular part of 

 prostate. m. muscles connecting the prostate with the body-wall. t. m. transverse muscles. I. m. longi- 

 tudinal muscles, cl. clitellar cells, v. cl. ventral termini of the clitellar region. 



41. Cross-section through a strongly contracted, fully matured specimen, through somite xviii, showing the copula- 



tory cushions as fully developed, as well as the clitellar cells on the ventral side. Unfortunately the only fully 

 developed specimen at my disposal had been badly contracted, hence the cells appear smaller than they would 

 have done in properly prepared specimens, c.c. copulatory cushions, a.m. arciform or fan-shaped muscu- 

 lar strands, which contract the copulatory region, i. t. m. interior transverse muscular strand, ending 

 resjiectively in the copulatory cushions and in the projecting ventral lobes of the body. Other letters as in 

 the last four figures. 



4'2. The body-wall viewed from the inner side of somites xvii, xviii and xix, showing the genital region of the left 

 side. //;-. m. prostate muscles connecting this organ with the body-wall. a. m. arciform muscles connecting 

 the copulatory cushion with the upi^er body-wall. c. c. copulatory cushion, sp. m. muscles connecting the 

 body-wall with the prostate at the junction with the spermduet. up. d. spermduct. 1 and 2 a. first and 

 second seta. v. c. ventral nerve cord. yl. pr. glandular prostate, m. pr. muscular prostate, s. m. smaller 

 ruuscles, fan-like arranged, confined entirely to the copulatory cushion, sp. d. p. spermiducal pore overlaid 

 by muscles, s. septa. 



43. A somewhat diagonal longitudinal section through the body- wall and copiilatory cushion in somite xviii. The 



section is parallel with the muscular fan of arciform muscles, passing through the cojiulatory cushion near 

 but not through the body-wall. Illustrating the arrangement of the muscular strands around the prostate in 

 the vicinity of the male pore. The letters indicate the same as in the preceding figure. 



44. A longitudinal section through the copulatory cushion and the body-wall, the section being almost vertical. 



pr. prostate, just leaving the arciform muscles, and immediately before bending down towards the prostate 

 pore. TO. muscles connecting the prostate with the body-wall. n. in. the entrance of the arciform muscles 

 into the copulatory cushion. 



4.5. A horizontal section of the body through somite xviii and the copulatory cushions, showing their size and 

 position, etc. 



