CLOACA AND SI'KR MATH EGA OF GYRINOPHILUS. 267 



"invasion" is used in the embryologic sense, as a downgrowth 

 of a bud or cord of cells of epithelial origin, not in the pathologic 

 sense implying unrestrained growth with loss of basement 

 membrane.) 



Glands in the larva of 10.5 cm. have been referred to above. 

 There are two groups of these; the tubules, as shown (Fig. 17 

 and 170) are very tiny and most of them are still solid cords. 

 The dorsal group is slightly better developed than the ventral. 

 The former, located caudal to the cellular area, is bilateral; 

 its tubules, numbering four to six on each side, are outgrowths 

 from the epithelium of the roof of the cloaca, and point dorso- 

 laterad. A ventral group of about the same number, is located 

 cephalad to the level of the cellular area; these are outgrowths 

 from the epithelium of the extreme ventral portion of the cloaca. 



Next in the series of stages is the smallest unmistakable 

 spermatheca, in an animal measuring 10.8 cm., captured in May; 

 a small stub of gill left on one side gives evidence of recent 

 transformation. It should be noted that this animal is further 

 developed than the two previously described, although the latter 

 were captured later in the summer (September and August 

 respectively). This young spermatheca consists of a larger 

 cellular area than that just described. The cells are arranged 

 in definite rows or cords perpendicular to the surface, and most 

 of the cords extending beyond the cellular area itself, terminate 

 in an expanded bulb with a minute lumen. There are ten or 

 twelve bulbs on each side, and they curve like plumes, dorso- 

 laterad, laterad and cephalad. The less well developed tubules 

 without definite bulbous expansions, are the most caudal of the 

 group. The whole organ occupies less than 0.4 mm. Of 

 especial interest is the lumen of the common tube. In its caudal 

 portion it is pyramidal in cross-section, with the base of the 

 pyramid dorsad (Fig. 18), and in its cephalic portion, rounded 

 but irregular (Fig. 19). Caudally it merges into the dorsal slit; 

 cephalicly it is replaced by the median fold which was observed 

 in earlier stages. Both groups of glands noted previously are 

 present. Though the ventral are but little more advanced in 

 development, the dorsal are now small tubules with bulbous ends, 

 similar in form to, but smaller than the spermathecal tubules. 

 Their subsequent fate will be discussed. 



