216 BULLETIN OF THE 



coils the filament is easily overlooked, except when the uncoiling is 

 already begun. At a somewat later stage the uncoiled filaments out- 

 number the oval bodies, and still later few or none of the latter are to 

 be found. The oval bodies are unquestionably single coiled spermatozoa 

 which suffer an unfolding and at length lie in the food-mass as out- 

 stretched male elements. They are often wrapped about the vitellus, 

 at other times thrown into irregular curves in the surrounding albumen. 

 The unfolding must be slow, for I have repeatedly watched in order to 

 discover the nature of the process, but have never succeeded in seeing 

 motion, either in the oval bodies or in the outstretched spermatozoa. 

 I have never failed to find spermatozoa when made an object of special 

 search. In some cases they are present in great quantities, even forming 

 extensive trains through different parts of the albumen. 



Neither the growth nor the structure of the spermatozoa has been 

 made the subject of extended observations. As regards their form it 

 may be seen from Fig. 94 that they are thread-like, gradually tapering 

 from immediately behind the " head " to the opposite extremity. They 

 may attain a length nearly equal to the diameter of the vitellus. The 

 " head " is flattened, oval, somewhat pointed a-t its free end, and when 

 seen side wise appears tongue-shaped and joined to the neck at a very 

 slight angle. The portion following the head has often a wavy course, 

 while the terminal part frequently remains in a loop. 



I once saw quite distinctly an interesting spermatozoon in the albu- 

 men of an egg already treated with reagents, and made at the time 

 (Aug. 15, 1878) a hasty sketch, which I have had reproduced in Fig. 94, 

 since it indicates the existence of an undulating memhrane. So far as I 

 am at present aware, this has never been observed before of the sperma- 

 tozoa of slugs. Ley dig {Lehrhuch d. Histologie, p. 533) says that hith- 

 erto (1857) zoosperms with undulating membrane have been found only 

 in the cases of Rotifers and Cypridse. Whether we have to do in the 

 case of Limax with dimorphic forms of the spermatozoa, I cannot say, 

 as I have given the subject no attention. The spermatozoon here figured 

 was motionless, so that I can only infer that the membrane figured un- 

 dulates in the active spermatozoon, after the manner known in the sala- 

 mander and other animals. The loop at the end of the tail in this case 

 seems to be very delicate; perhaps it is formed exclusively by the thin 

 membrane.* ^p 



* Sept. 1, 1880. Gibbes {'80) has recently demonstrated the existence of the 

 vibratile membrane in the case of several vertebrates, and some invertebrates. 

 Among the latter is Helix ; I am thus the more confident that it is really an un- 

 dulating membrane which I have seen in Limax. 



